Dr Igor Marko

Research Staff

Qualifications: PhD

Email:
Phone: Work: 01483 68 6161
Room no: 11 SE 01

Further information

Biography

Igor Pavlovich Marko was born in 1974 in Belarus. He graduated with distinction from the department of quantum radiophysics and optoelectronics of the Belarusian State University in 1996. From 1996 until 2001 he studied the optical properties of ZnSe- and GaN-based wide bandgap semiconductors and optically pumped lasers in the Laboratory of Semiconductor Optics of B. I. Stepanov Institute of Physics of the Belarusian Academy of Sciences. He received the degree of PhD in 2000 (thesis: "Optically Pumped Lasers Based on ZnSe Epitaxial Layers and ZnMgSSe/ZnSe Quantum Well Heterostructures"). Since 2001 have been studying the properties of near-IR and mid-IR III-V based interband quantum dots, quantum well lasers, short-wavelength (<3.5um) quantum cascade lasers, InGaNAs avalanche photodiodes at the University of Surrey. Most recent activity includes developing of a new III-V material systems containing Bi.

Research Interests

My current research interests includes III-V visible light-emitting diodes and lasers, near-infrared quantum dot and quantum well lasers for telecommunications, avalanche photo-diodes for 1.3-1.5μm spectral range, mid-infrared interband and quantum cascade lasers. Most recent projects include developing of a new III-V material systems containing Bi (GaAsBi/GaAs, InGaAsBi/InP).

Publications

Highlights

  • Ludewig P, Knaub N, Hossain N, Reinhard S, Nattermann L, Marko IP, Jin SR, Hild K, Chatterjee S, Stolz W, Sweeney SJ, Volz K. (2013) 'Electrical injection Ga(AsBi)/(AlGa)As single quantum well laser'. Applied Physics Letters, 102 (24)

    Abstract

    The Ga(AsBi) material system opens opportunities in the field of high efficiency infrared laser diodes. We report on the growth, structural investigations, and lasing properties of dilute bismide Ga(AsBi)/(AlGa)As single quantum well lasers with 2.2% Bi grown by metal organic vapor phase epitaxy on GaAs (001) substrates. Electrically injected laser operation at room temperature is achieved with a threshold current density of 1.56 kA/cm2 at an emission wavelength of ∼947 nm. These results from broad area devices show great promise for developing efficient IR laser diodes based on this emerging materials system. © 2013 AIP Publishing LLC.

  • Marko IP, Batool Z, Hild K, Jin SR, Hossain N, Hosea TJC, Sweeney SJ, Hosea TJC, Petropoulos JP, Zhong Y, Dongmo PB, Zide JMO. (2012) 'Temperature and Bi-concentration dependence of the bandgap and spin-orbit splitting in InGaBiAs/InP semiconductors for mid-infrared applications'. Applied Physics Letters, 101 (22)

    Abstract

    Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ > E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ (x, T) in InGa BiAs/InP samples for 0 x 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence of a decreased dE/dT (≈0.34 ± 0.06 meV/K in all samples) we find Δ > E for x > 3.3-4.3. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 American Institute of Physics.

  • Sayid SA, Marko IP, Sweeney SJ, Barrios P, Poole PJ. (2010) 'Efficiency limiting processes in 1.55 mu m InAs/InP-based quantum dots lasers'. APPLIED PHYSICS LETTERS, 97 (16) Article number ARTN 161104
  • Crowley MT, Marko IP, Masse NF, Andreev AD, Tomic S, Sweeney SJ, O'Reilly EP, Adams AR. (2009) 'The Importance of Recombination via Excited States in InAs/GaAs 1.3 mu m Quantum-Dot Lasers'. IEEE J SEL TOP QUANT, 15 (3), pp. 799-807.

    Abstract

    The temperature dependence of the radiative and nonradiative components of the threshold current density of 1.3 mu m InAs/GaAs quantum-dot lasers have been analyzed both experimentally and theoretically. It is shown that the weak temperature variation measured for the radiative current density arises because the optical matrix element for excited state transitions is significantly smaller than for the ground state transition. In contrast, nonradiative Auger recombination can have a similar probability for transitions involving excited states as for those involving ground state carriers. The sharp increase in the threshold current density at high temperatures follows the temperature variation of the cubed threshold carrier density confirming that Auger recombination is the dominant recombination mechanism in these devices at room temperature.

  • Masse NF, Homeyer E, Marko IP, Adams AR, Sweeney SJ, Dehaese O, Piron R, Grillot F, Loualiche S. (2007) 'Temperature and pressure dependence of the recombination processes in 1.5 mu m InAs/InP (311)B quantum dot lasers'. APPLIED PHYSICS LETTERS, 91 (13) Article number ARTN 131113
  • Masse NF, Sweeney SJ, Marko IP, Adams AR, Hatori N, Sugawara M. (2006) 'Temperature dependence of the gain in p-doped and intrinsic 1.3 mu m InAs/GaAs quantum dot lasers'. APPLIED PHYSICS LETTERS, 89 (19) Article number ARTN 191118

Journal articles

  • Broderick C, Jin S, Marko I, Hild K, Ludewig P, Bushell ZL, Stolz W, Rorison J, O’Reilly E, Volz K, Sweeney S . (2017) 'GaAs1−xBix/GaNyAs1−y type-II quantum wells: novel strain-balanced heterostructures for GaAs-based near- and mid-infrared photonics'. Scientific Reports, 7 Article number 46371

    Abstract

    The potential to extend the emission wavelength of photonic devices further into the near- and midinfrared via pseudomorphic growth on conventional GaAs substrates is appealing for a number of communications and sensing applications. We present a new class of GaAs-based quantum well (QW) heterostructure that exploits the unusual impact of Bi and N on the GaAs band structure to produce type-II QWs having long emission wavelengths with little or no net strain relative to GaAs, while also providing control over important laser loss processes. We theoretically and experimentally demonstrate the potential of GaAs1−xBix/GaNyAs1−y type-II QWs on GaAs and show that this approach offers optical emission and absorption at wavelengths up to ~3 μm utilising strain-balanced structures, a first for GaAs-based QWs. Experimental measurements on a prototype GaAs0.967Bi0.033/GaN0.062As0.938 structure, grown via metal-organic vapour phase epitaxy, indicate good structural quality and exhibit both photoluminescence and absorption at room temperature. The measured photoluminescence peak wavelength of 1.72 μm is in good agreement with theoretical calculations and is one of the longest emission wavelengths achieved on GaAs to date using a pseudomorphically grown heterostructure. These results demonstrate the significant potential of this new class of III-V heterostructure for longwavelength applications.

  • Eales T, Marko I, Ikyo B, Adams AR, Arafin S, Sprengel S, Amann M, Sweeney S . (2017) 'Wavelength dependence of efficiency limiting mechanisms in Type-I Mid-infrared GaInAsSb/GaSb lasers'. IEEE Journal of Selected Topics in Quantum Electronics, 23 (6)

    Abstract

    The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at 2.3 μm, 2.6 μm and 2.9 μm, are investigated. Temperature characterization techniques and measurements under hydrostatic pressure identify an Auger process as the dominant non-radiative recombination mechanism in these devices. The results are supplemented with hydrostatic pressure measurements from three additional type-I GaInAsSb lasers, extending the wavelength range under investigation from 1.85-2.90 μm. Under hydrostatic pressure, contributions from the CHCC and CHSH Auger mechanisms to the threshold current density can be investigated separately. A simple model is used to fit the non-radiative component of the threshold current density, identifying the dominance of the different Auger losses across the wavelength range of operation. The CHCC mechanism is shown to be the dominant non-radiative process at longer wavelengths (> 2 μm). At shorter wavelengths (< 2 μm) the CHSH mechanism begins to dominate the threshold current, as the bandgap approaches resonance with the spin-orbit split-off band.

  • Marko I, Sweeney S . (2017) 'Progress towards III-V-Bismide Alloys for Near- and Mid-Infrared Laser Diodes'. IEEE Journal of Selected Topics in Quantum Electronics, 23 (6) Article number 1501512

    Abstract

    Bismuth-containing III-V alloys open-up a range of possibilities for practical applications in semiconductor lasers, photovoltaics, spintronics, photodiodes and thermoelectrics. Of particular promise for the development of semiconductor lasers is the possibility to grow GaAsBi laser structures such that the spin-orbit-splitting energy (ΔSO) is greater than the bandgap (Eg) in the active region for devices operating around the telecom wavelength of 1.55 μm, thereby suppressing the dominant efficiency-limiting loss processes in such lasers, namely Auger recombination and inter-valence band absorption (IVBA). The ΔSO > Eg band structure is present in GaAsBi alloys containing > 10% Bi, at which composition the alloy band gap is close to 1.55 μm on a GaAs substrate making them an attractive candidate material system for the development of highly efficient, uncooled GaAs-based lasers for telecommunications. Here we discuss progress towards this goal and present a comprehensive set of data on the properties of GaAsBi lasers including optical gain and absorption characteristics and the dominant carrier recombination processes in such systems. Finally, we briefly review the potential of GaAsBiN and InGaAsBi material systems for near- and mid-infrared photonic devices on GaAs and InP platforms, respectively.

  • Marko I, Broderick CA, Jin S, Ludewig P, Stolz W, Volz K, Rorison JM, O’Reilly EP, Sweeney SJ. (2016) 'Optical gain in GaAsBi/GaAs quantum well diode lasers'. Scientific Reports, 6

    Abstract

    Electrically pumped GaAsBi/GaAs quantum well lasers are a promising new class of near-infrared devices where, by use of the unusual band structure properties of GaAsBi alloys, it is possible to suppress the dominant energy-consuming Auger recombination and inter-valence band absorption loss mechanisms, which greatly impact upon the device performance. Suppression of these loss mechanisms promises to lead to highly efficient, uncooled operation of telecommunications lasers, making GaAsBi system a strong candidate for the development of next-generation semiconductor lasers. In this report we present the first experimentally measured optical gain, absorption and spontaneous emission spectra for GaAsBi-based quantum well laser structures. We determine internal optical losses of 10–15 cm−1 and a peak modal gain of 24 cm−1, corresponding to a material gain of approximately 1500 cm−1 at a current density of 2 kA cm−2. To complement the experimental studies, a theoretical analysis of the spontaneous emission and optical gain spectra is presented, using a model based upon a 12-band k.p Hamiltonian for GaAsBi alloys. The results of our theoretical calculations are in excellent quantitative agreement with the experimental data, and together provide a powerful predictive capability for use in the design and optimisation of high efficiency lasers in the infrared.

  • Marko I, Sweeney S, Hild K. (2016) 'Temperature stable mid-infrared GaInAsSb/GaSb Vertical Cavity Surface Emitting Lasers (VCSELs)'. Scientific Reports, 6 Article number 19595

    Abstract

    GaInAsSb/GaSb based quantum well vertical cavity surface emitting lasers (VCSELs) operating in mid-infrared spectral range between 2 and 3 micrometres are of great importance for low cost gas monitoring applications. This paper discusses the efficiency and temperature sensitivity of the VCSELs emitting at 2.6 μm and the processes that must be controlled to provide temperature stable operation. We show that non-radiative Auger recombination dominates the threshold current and limits the device performance at room temperature. Critically, we demonstrate that the combined influence of non-radiative recombination and gain peak – cavity mode de-tuning determines the overall temperature sensitivity of the VCSELs. The results show that improved temperature stable operation around room temperature can only be achieved with a larger gain peak – cavity mode de-tuning, offsetting the significant effect of increasing non-radiative recombination with increasing temperature, a physical effect which must be accounted for in mid-infrared VCSEL design.

  • Marko IP, Jin SR, Hild K, Batool Z, Bushell ZL, Ludewig P, Stolz W, Volz K, Butkute R, Pacebutas V, Geizutis A, Krotkus A, Sweeney SJ. (2015) 'Properties of hybrid MOVPE/MBE grown GaAsBi/GaAs based near-infrared emitting quantum well lasers'. SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 30 (9) Article number ARTN 094008
    [ Status: Accepted ]
  • Marko I, Read G, Hossain N, Sweeney S . (2015) 'Physical Properties and Characteristics of III-V Lasers on Silicon'. IEEE Journal of Selected Topics in Quantum Electronics, 21 (6) Article number 1502208

    Abstract

    The development of laser technology based on silicon continues to be of key importance for the advancement of electronic-photonic integration offering the potential for high data rates and reduced energy consumption. Progress was initially hindered due to the inherent indirect band gap of silicon. However, there has been considerable progress in developing ways of incorporating high gain III-V based direct band gap materials onto silicon, bringing about the advantages of both materials. In this paper, we introduce the need for lasers on silicon and review some of the main approaches for the integration of III-V active regions, including direct epitaxial growth, hybrid integration, defect blocking layers and quantum dots. We then discuss the roles of different carrier recombination processes on the performance of devices formed using both wafer fusion and direct epitaxial approaches.

  • Adams AR, Marko I, Mukherjee J, Stolojan V, Sweeney S, Gocalinska A, Pelucchi E, Thomas K, Corbett B. (2015) 'Semiconductor Quantum Well Lasers With a Temperature-Insensitive Threshold Current'. IEEE Journal of Selected Topics in Quantum Electronics, 21 (6) Article number 150080

    Abstract

    This paper proposes and demonstrates a new multiquantum well (MQW) laser structure with a temperature-insensitive threshold current and output power. Normally, the mechanisms that cause the threshold current (Ith) of semiconductor lasers to increase with increasing temperature T (thermal broadening of the gain spectrum, thermally activated carrier escape, Auger recombination, and intervalence band absorption) act together to cause Ith to increase as T increases. However, in the design presented here, carriers thermally released from some of the QWs are fed to the other QWs so that these mechanisms compensate rather than augment one another. The idea is in principle applicable to a range of materials systems, structures, and operating wavelengths. We have demonstrated the effect for the first time in 1.5 μm GaInAsP/InP Fabry-Perot cavity edge-emitting lasers. The results showed that it is possible to keep the threshold current constant over a temperature range of about 100 K and that the absolute temperature over which the plateau occurred could be adjusted easily by redesigning the quantum wells and the barriers between them. TEM studies of the structures combined with measurements of the electroluminescent intensities from the wells are presented and explain well the observed effects.

  • Marko IP, Sweeney SJ. (2015) 'Optical and electronic processes in semiconductor materials for device applications'. Springer Series in Materials Science, 203, pp. 253-297.

    Abstract

    In this chapter we consider the important optical and electronic processes which influence the properties of semiconductor photonic devices. Focussing on a number of material systems, we describe semiconductor materials and structures used for light-emitting applications (lasers and LEDs) operating in a wide spectral range from visible to mid-infrared. The main carrier recombination mechanisms in semiconductor devices are discussed and experimental methodologies for measuring and analysing these mechanisms are introduced. Near infra-red (IR) quantum well (QW) lasers are discussed in depth considering several new approaches to overcome fundamental performance issues. Different approaches for the longer wavelength (mid-IR) semiconductor devices are reviewed showing the benefits of different approaches to material and device design where energy efficiency and high temperature operation are the principal concerns. Finally, semiconductor lasers and LEDs for the visible spectral range are briefly introduced in terms of the most important issues related to their performance.

  • Marko IP, Bushell ZL, Jin SR, Hild K, Batool Z, Sweeney SJ, Ludewig P, Reinhard S, Nattermann L, Stolz W, Volz K. (2014) 'Physical properties and optimization of GaBiAs/(Al)GaAs based near-infrared laser diodes grown by MOVPE with up to 4.4% Bi'. Journal of Physics D: Applied Physics, 47 (34)

    Abstract

    This paper reports on progress in the development of GaAsBi/(Al)GaAs based lasers grown using metal-organic vapour phase epitaxy and focuses on the underlying processes governing their efficiency and temperature dependence. Room temperature lasing has been achieved in devices with 2.2% Bi and lasing in devices with 4.4% Bi was observed up to 180 K. We show that the device performance can be improved by optimizing both electrical and optical confinement in the laser structures. Analysis of the temperature dependence of the threshold current together with pure spontaneous emission and high hydrostatic pressure measurements indicate that device performance is currently dominated by non-radiative recombination through defects (>80% of the threshold current at room temperature in 2.2% Bi samples) and that to further improve the device performance and move towards longer wavelengths for optical telecommunications (1.3-1.5 μ m) further effort is required to improve and optimize material quality. © 2014 IOP Publishing Ltd.

  • Chai GMT, Hosea TJC, Fox NE, Hild K, Ikyo AB, Marko IP, Sweeney SJ, Bachmann A, Arafin S, Amann M-C. (2014) 'Characterization of 2.3 mu m GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance'. JOURNAL OF APPLIED PHYSICS, 115 (1) Article number ARTN 013102
  • Sweeney SJ, Marko IP, Jin SR, Hild K, Batool Z, Ludewig P, Natterman L, Bushell Z, Stolz W, Volz K, Broderick CA, Usman M, Harnedy PE, Oreilly EP, Butkute R, Pacebutas V, Geiutis A, Krotkus A. (2014) 'Electrically injected GaAsBi quantum well lasers'. Conference Digest - IEEE International Semiconductor Laser Conference, , pp. 80-81.

    Abstract

    GaAsBi QWs have the potential to remove inherent recombination losses thereby increasing the efficiency and reducing the temperature sensitivity of near-infrared telecommunications lasers. GaAsBi QW lasers are reported and prospects for 1550nm operation are discussed.

  • Marko IP, Adams AR, Massé NF, Sweeney SJ. (2014) 'Effect of non-pinned carrier density above threshold in InAs quantum dot and quantum dash lasers'. IET Optoelectronics, 8 (2), pp. 88-93.

    Abstract

    The impact of carrier density non-pinning above threshold on laser performance is studied in different quantum dot/dash lasers with room temperature emission wavelengths of 0.98-1.52 μm. Owing to inhomogeneity in the active region, the non-pinning may be important even above room temperature because of the non-thermal carrier distribution between the dots. This has a large impact on the external differential efficiency and the output power of the devices. In the presence of non-radiative recombination, non-pinning will further decrease the output power and the slope efficiency because of a significant reduction in the number of carriers available for stimulated emission. © The Institution of Engineering and Technology 2014.

  • Tan SL, Soong WM, Green JE, Steer MJ, Zhang S, Tan LJJ, Ng JS, Marko IP, Sweeney SJ, Adams AR, Allam J, David JPR. (2013) 'Experimental evaluation of impact ionization in dilute nitride GaInNAs diodes'. Applied Physics Letters, 103 (10)

    Abstract

    The anomalous behavior of impact ionization in dilute-nitride GaInNAs photodiodes with a range of nitrogen content below 4% is investigated. The ratio of hole- and electron-initiated ionization coefficients, k = β/α, is enhanced by a factor up to ∼4 with increasing nitrogen content. The absolute ionization coefficients are suppressed by up to two orders of magnitude at low electric fields in samples with 3% N. The narrow band gap, suppressed impact ionization, and increased breakdown voltage characteristics of GaInNAs make it a suitable material for use as part of a composite collector in GaAs-based heterojunction bipolar transistors. © 2013 AIP Publishing LLC.

  • Pal J, Migliorato MA, Li C-K, Wu Y-R, Crutchley BG, Marko IP, Sweeney SJ. (2013) 'Enhancement of efficiency of InGaN-based light emitting diodes through strain and piezoelectric field management'. Journal of Applied Physics, 114 (7)

    Abstract

    We report calculations of the strain dependence of the piezoelectric field within InGaN multi-quantum wells light emitting diodes. Such fields are well known to be a strong limiting factor of the device performance. By taking into account the nonlinear piezoelectric coefficients, which in particular cases predict opposite trends compared to the commonly used linear coefficients, a significant improvement of the spontaneous emission rate can be achieved as a result of a reduction of the internal field. We propose that such reduction of the field can be obtained by including a metamorphic InGaN layer below the multiple quantum well active region. © 2013 AIP Publishing LLC.

  • Ludewig P, Knaub N, Hossain N, Reinhard S, Nattermann L, Marko IP, Jin SR, Hild K, Chatterjee S, Stolz W, Sweeney SJ, Volz K. (2013) 'Electrical injection Ga(AsBi)/(AlGa)As single quantum well laser'. Applied Physics Letters, 102 (24)

    Abstract

    The Ga(AsBi) material system opens opportunities in the field of high efficiency infrared laser diodes. We report on the growth, structural investigations, and lasing properties of dilute bismide Ga(AsBi)/(AlGa)As single quantum well lasers with 2.2% Bi grown by metal organic vapor phase epitaxy on GaAs (001) substrates. Electrically injected laser operation at room temperature is achieved with a threshold current density of 1.56 kA/cm2 at an emission wavelength of ∼947 nm. These results from broad area devices show great promise for developing efficient IR laser diodes based on this emerging materials system. © 2013 AIP Publishing LLC.

  • Aldukhayel A, Jin SR, Marko IP, Sweeney SJ, Zhang SY, Revin DG, Cockburn JW. (2013) 'Investigations of carrier scattering into L-valley in λ=3.5μm InGaAs/AlAs(Sb) quantum cascade lasers using high hydrostatic pressure'. Physica Status Solidi (B) Basic Research, 250 (4), pp. 693-697.

    Abstract

    In order to identify the performance limitations of InGaAs/AlAs(Sb) quantum cascade lasers, experimental investigations of the temperature and pressure dependencies of the threshold current (I) were undertaken. Using the theoretical optical phonon current (I) and carrier leakage (I) to fit the measured threshold current at various pressures, we show that the electron scattering from the top lasing level to the upper L-minima gives rise to the increase in I with pressure and temperature. It was found that this carrier leakage path accounts for approximately 3% of I at RT and is negligible at 100K. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Crutchley BG, Marko IP, Sweeney SJ, Pal J, Migliorato MA. (2013) 'Optical properties of InGaN-based LEDs investigated using high hydrostatic pressure dependent techniques'. Physica Status Solidi (B) Basic Research, 250 (4), pp. 698-702.

    Abstract

    High pressure electroluminescence (EL) measurements were carried out on blue and green emitting InGaN-based light emitting diodes (LEDs). The weak pressure coefficient of the peak emission energy of the LEDs is found to increase with increasing injection current. Such behaviour is consistent with an enhancement of the piezoelectric fields under high pressure which become increasingly screened at high currents. A subsequent increase in the quantum confined Stark effect (QCSE) is expected to cause a reduction of the light output power as pressure is applied at a fixed low current density (∼10Acm). A similar proportional reduction of light output power as pressure is applied at a fixed high current density (260Acm) suggests that there is a non-radiative loss process in these devices which is relatively insensitive to pressure. Such behaviour is shown to be consistent with a defect-related recombination process which increases with increasing injection. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Crutchley BG, Marko IP, Sweeney SJ. (2013) 'The influence of temperature on the recombination processes in blue and green InGaN LEDs'. Physica Status Solidi (C) Current Topics in Solid State Physics, 2 (12)

    Abstract

    A temperature dependent investigation into the efficiency droop effect in blue and green InGaN light-emitting diodes (LEDs) is presented. The efficiency droop effect is observed to be the strongest at low temperatures in both blue and green LEDs. We show such behaviour is consistent with a reduced hole injection rate resulting in an increased concentration of electron leakage from the quantum wells. Spectral measurements demonstrate that the emission peak has an "s-shape" dependence on tem-perature and a full-width at half-maximum which increases with decreasing temperature below 100 K. Such observations indicate the importance of carrier localization in the InGaN LEDs. At temperatures where hole injection is not problematic the efficiency droop is the result of carrier delocalization and subsequent defect related recombination with increasing current injection. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Crutchley B, Marko I, Adams AR, Sweeney S . (2013) 'Investigating the efficiency limitations of GaN-based emitters'. 2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013,

    Abstract

    In this study low temperature and high pressure techniques have been used to investigate the recombination processes taking place in InGaN-based quantum well light emitting diodes (LEDs) which have emission across the blue-green region. Despite relatively high peak efficiencies of the GaN-based emitters, there remain issues relating to the strong efficiency reduction at higher currents that are required for normal operation in most applications. It is observed that there is a relative reduction in efficiency as injection current is increased in a phenonmenon which is known as efficiency droop. There are three main arguments for the cause of efficiency droop that are discussed in the literature: non-radiative Auger recombination, carrier leakage and a defect-related loss mechanism. In spite of extensive research to date, there is little agreement on the cause of efficiency droop as most experiments can only measure the overall efficiency behaviour leading to difficulties in determining the individual contributions from the different loss mechanisms. © 2013 IEEE.

  • Tan S, Hunter C, Zhang S, Tan L, Goh Y, Ng J, David J, Marko I, Sweeney S, Adams AR, Allam J . (2012) 'Improved optoelectronic properties of rapid thermally annealed dilute nitride GaInNAs photodetectors'. Journal of Electronic Materials, 41 (12), pp. 3393-3401.

    Abstract

    We investigate the optical and electrical characteristics of GaInNAs/GaAs long-wavelength photodiodes grown under varying conditions by molecular beam epitaxy and subjected to postgrowth rapid thermal annealing (RTA) at a series of temperatures. It is found that the device performance of the nonoptimally grown GaInNAs p-i-n structures, with nominal compositions of 10% In and 3.8% N, can be improved significantly by the RTA treatment to match that of optimally grown structures. The optimally annealed devices exhibit overall improvement in optical and electrical characteristics, including increased photoluminescence brightness, reduced density of deep-level traps, reduced series resistance resulting from the GaAs/GaInNAs heterointerface, lower dark current, and significantly lower background doping density, all of which can be attributed to the reduced structural disorder in the GaInNAs alloy.© 2012 TMS.

  • Marko IP, Batool Z, Hild K, Jin SR, Hossain N, Hosea TJC, Sweeney SJ, Hosea TJC, Petropoulos JP, Zhong Y, Dongmo PB, Zide JMO. (2012) 'Temperature and Bi-concentration dependence of the bandgap and spin-orbit splitting in InGaBiAs/InP semiconductors for mid-infrared applications'. Applied Physics Letters, 101 (22)

    Abstract

    Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ > E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ (x, T) in InGa BiAs/InP samples for 0 x 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence of a decreased dE/dT (≈0.34 ± 0.06 meV/K in all samples) we find Δ > E for x > 3.3-4.3. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 American Institute of Physics.

  • Blume G, Hild K, Marko IP, Hosea TJC, Yu SQ, Chaparro SA, Samal N, Johnson SR, Zhang YH, Sweeney SJ. (2012) 'Cavity mode gain alignment in GaAsSb-based near-infrared vertical cavity lasers studied by spectroscopy and device measurements'. Journal of Applied Physics, 112 (3)

    Abstract

    We present a combination of spectroscopy and device measurements on GaAsSb/GaAs vertical-cavity surface-emitting laser (VCSEL) structures to determine the temperature at which the wavelength of the VCSEL cavity mode (CM) aligns with that of the quantum well (QW) ground-state transition (GST), and therefore the gain peak. We find that, despite the achievement of room temperature (RT) continuous wave lasing in VCSEL devices, the QW transition and the CM are actually slightly misaligned at this temperature; room temperature electroluminescence measurements from a cleaved edge of the VCSEL wafer indicate that the 300 K QW GST energy is at 0.975 ± 0.005 eV, while the CM measured in the VCSEL surface reflectivity spectra is at 0.9805 ± 0.0002 eV. When the wafer sample is cooled, the CM and QW GST can be brought into alignment at 270 ± 10 K, as confirmed by temperature-dependent electro-modulated reflectance (ER) and edge-electroluminescence spectroscopic studies. This alignment temperature is further confirmed by comparing the temperature dependence of the emission energy of a fabricated VCSEL device with that of an edge-emitting laser structure with a nominally identical active region. The study suggests that for further device improvement, the room temperature CM and QW GST energies should be more closely matched and both designed to a smaller energy of about 0.95 eV, somewhat closer to the 1.31 μm target. The study amply demonstrates the usefulness of non-destructive ER characterisation techniques in VCSEL manufacturing with GaAsSb-based QWs. © 2012 American Institute of Physics.

  • Hossain N, Marko IP, Jin SR, Hild K, Sweeney SJ, Lewis RB, Beaton DA, Tiedje T. (2012) 'Recombination mechanisms and band alignment of GaAs1-xBix/GaAs light emitting diodes'. APPLIED PHYSICS LETTERS, 100 (5) Article number ARTN 051105
  • Reed GT, Thomson DJ, Gardes FY, Hu Y, Owens N, Yang X, Petropoulos P, Debnath K, O'Faolain L, Krauss TF, Lever L, Ikonic Z, Kelsall RW, Myronov M, Leadley DR, Marko IP, Sweeney SJ, Cox DC, Brimont A, Sanchis P, Duan G-H, Le Liepvre A, Jany C, Lamponi M, Make D, Lelarge F, Fedeli JM, Messaoudene S, Keyvaninia S, Roelkens G, Van Thourhout D, Liu S. (2012) 'High performance silicon optical modulators'. Proceedings of SPIE - The International Society for Optical Engineering, 8564

    Abstract

    In this work we present results from high performance silicon optical modulators produced within the two largest silicon photonics projects in Europe; UK Silicon Photonics (UKSP) and HELIOS. Two conventional MZI based optical modulators featuring novel self-aligned fabrication processes are presented. The first is based in 400nm overlayer SOI and demonstrates 40Gbit/s modulation with the same extinction ratio for both TE and TM polarisations, which relaxes coupling requirements to the device. The second design is based in 220nm SOI and demonstrates 40Gbits/s modulation with a 10dB extinction ratio as well modulation at 50Gbit/s for the first time. A ring resonator based optical modulator, featuring FIB error correction is presented. 40Gbit/s, 32fJ/bit operation is also shown from this device which has a 6um radius. Further to this slow light enhancement of the modulation effect is demonstrated through the use of both convention photonic crystal structures and corrugated waveguides. Fabricated conventional photonic crystal modulators have shown an enhancement factor of 8 over the fast light case. The corrugated waveguide device shows modulation efficiency down to 0.45V.cm compared to 2.2V.cm in the fast light case. 40Gbit/s modulation is demonstrated with a 3dB modulation depth from this device. Novel photonic crystal based cavity modulators are also demonstrated which offer the potential for low fibre to fibre loss. In this case preliminary modulation results at 1Gbit/s are demonstrated. Ge/SiGe Stark effect devices operating at 1300nm are presented. Finally an integrated transmitter featuring a III-V source and MZI modulator operating at 10Gbit/s is presented. © 2012 SPIE.

  • Tan SL, Hunter CJ, Zhang S, Tan LJJ, Goh YL, Ng JS, David JPR, Marko IP, Sweeney SJ, Adams AR, Allam J. (2012) 'Improved Optoelectronic Properties of Rapid Thermally Annealed Dilute Nitride GaInNAs Photodetectors'. Journal of Electronic Materials, , pp. 1-9.

    Abstract

    We investigate the optical and electrical characteristics of GaInNAs/GaAs long-wavelength photodiodes grown under varying conditions by molecular beam epitaxy and subjected to postgrowth rapid thermal annealing (RTA) at a series of temperatures. It is found that the device performance of the nonoptimally grown GaInNAs p -i-n structures, with nominal compositions of 10% In and 3.8% N, can be improved significantly by the RTA treatment to match that of optimally grown structures. The optimally annealed devices exhibit overall improvement in optical and electrical characteristics, including increased photoluminescence brightness, reduced density of deep-level traps, reduced series resistance resulting from the GaAs/GaInNAs heterointerface, lower dark current, and significantly lower background doping density, all of which can be attributed to the reduced structural disorder in the GaInNAs alloy. © 2012 TMS.

  • Lever L, Hu Y, Myronov M, Liu X, Owens N, Gardes FY, Marko IP, Sweeney SJ, Ikonic Z, Leadley DR, Reed GT, Kelsall RW. (2011) 'Modulation of the absorption coefficient at 1.3 mu m in Ge/SiGe multiple quantum well heterostructures on silicon'. OPTICS LETTERS, 36 (21), pp. 4158-4160.

    Abstract

    We report modulation of the absorption coefficient at 1.3 μm in Ge/SiGe multiple quantum well heterostructures on silicon via the quantum-confined Stark effect. Strain engineering was exploited to increase the direct optical bandgap in the Ge quantum wells. We grew 9 nm-thick Ge quantum wells on a relaxed Si0.22Ge0.78 buffer and a contrast in the absorption coefficient of a factor of greater than 3.2 was achieved in the spectral range 1290–1315 nm.

  • Cheetham KJ, Krier A, Marko IP, Aldukhayel A, Sweeney SJ. (2011) 'Direct evidence for suppression of Auger recombination in GaInAsSbP/InAs mid-infrared light-emitting diodes'. APPL PHYS LETT, 99 (14) Article number 141110
  • Hild K, Marko IP, Johnson SR, Yu S-Q, Zhang Y-H, Sweeney SJ. (2011) 'Influence of de-tuning and non-radiative recombination on the temperature dependence of 1.3 mu m GaAsSb/GaAs vertical cavity surface emitting lasers'. APPLIED PHYSICS LETTERS, 99 (7) Article number ARTN 071110
  • Ikyo BA, Marko IP, Adams AR, Sweeney SJ, Canedy CL, Vurgaftman I, Kim CS, Kim M, Bewley WW, Meyer JR. (2011) 'Temperature dependence of 4.1 mu m mid-infrared type II "W" interband cascade lasers'. APPLIED PHYSICS LETTERS, 99 (2) Article number ARTN 021102
  • Tan SL, Zhang S, Soong WM, Goh YL, Tan LJJ, Ng JS, David JPR, Marko IP, Adams AR, Sweeney SJ, Allam J. (2011) 'GaInNAsSb/GaAs Photodiodes for Long-Wavelength Applications'. IEEE ELECTRON DEVICE LETTERS, 32 (7), pp. 919-921.
  • Sayid SA, Marko IP, Sweeney SJ, Barrios P, Poole PJ. (2010) 'Efficiency limiting processes in 1.55 mu m InAs/InP-based quantum dots lasers'. APPLIED PHYSICS LETTERS, 97 (16) Article number ARTN 161104
  • Sayid SA, Marko IP, Cannard PJ, Chen X, Rivers LJ, Lealman IF, Sweeney SJ. (2010) 'Thermal Characteristics of 1.55-mu m InGaAlAs Quantum Well Buried Heterostructure Lasers'. IEEE JOURNAL OF QUANTUM ELECTRONICS, 46 (5), pp. 700-705.
  • Marko IP, Aldukhayel AM, Adams AR, Sweeney SJ, Teissier R, Baranov AN, Tomić S. (2010) 'Physical properties of short wavelength 2.6μm InAs/AlSb-based quantum cascade lasers'. Conference Digest - IEEE International Semiconductor Laser Conference, , pp. 95-96.

    Abstract

    We used high hydrostatic pressure techniques to understand the deteriorating temperature performance with decreasing wavelength of short wavelength quantum cascade lasers. Influence of inter-valley scattering and distribution of the electron wave functions will be discussed.

  • Crowley MT, Marko IP, Masse NF, Andreev AD, Tomic S, Sweeney SJ, O'Reilly EP, Adams AR. (2009) 'The Importance of Recombination via Excited States in InAs/GaAs 1.3 mu m Quantum-Dot Lasers'. IEEE J SEL TOP QUANT, 15 (3), pp. 799-807.

    Abstract

    The temperature dependence of the radiative and nonradiative components of the threshold current density of 1.3 mu m InAs/GaAs quantum-dot lasers have been analyzed both experimentally and theoretically. It is shown that the weak temperature variation measured for the radiative current density arises because the optical matrix element for excited state transitions is significantly smaller than for the ground state transition. In contrast, nonradiative Auger recombination can have a similar probability for transitions involving excited states as for those involving ground state carriers. The sharp increase in the threshold current density at high temperatures follows the temperature variation of the cubed threshold carrier density confirming that Auger recombination is the dominant recombination mechanism in these devices at room temperature.

  • Masse NF, Marko IP, Adams AR, Sweeney SJ. (2009) 'Temperature insensitive quantum dot lasers: are we really there yet?'. JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, London, ENGLAND: 20, pp. 272-276.
  • Masse NF, Homeyer E, Marko IP, Adams AR, Sweeney SJ, Dehaese O, Piron R, Grillot F, Loualiche S. (2007) 'Temperature and pressure dependence of the recombination processes in 1.5 mu m InAs/InP (311)B quantum dot lasers'. APPLIED PHYSICS LETTERS, 91 (13) Article number ARTN 131113
  • Masse NF, Sweeney SJ, Marko IP, Adams AR, Hatori N, Sugawara M. (2006) 'Temperature dependence of the gain in p-doped and intrinsic 1.3 mu m InAs/GaAs quantum dot lasers'. APPLIED PHYSICS LETTERS, 89 (19) Article number ARTN 191118
  • Hild K, Sweeney SJ, Wright S, Lock DA, Jin SR, Marko IP, Johnson SR, Chaparro SA, Yu S-Q, Zhang Y-H. (2006) 'Carrier recombination in 1.3 mu m GaAsSb/GaAs quantum well lasers'. APPLIED PHYSICS LETTERS, 89 (17) Article number ARTN 173509
  • Marko IP, Masse NF, Sweeney SJ, Andreev AD, Adams AR, Hatori N, Sugawara M. (2005) 'Carrier transport and recombination in p-doped and intrinsic 1.3 mu m InAs/GaAs quantum-dot lasers'. APPLIED PHYSICS LETTERS, 87 (21) Article number ARTN 211114
  • Marko IP, Andreev AD, Adams AR, Krebs R, Reithmaier JP, Forchel A. (2003) 'The role of Auger recombination in InAs 1.3-/mu m quantum-dot lasers investigated using high hydrostatic pressure'. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 9 (5), pp. 1300-1307.
  • Marko I, Andreev AD, Adams AR, Krebs R, Reithmaier J, Forchel A. (2003) 'The Role of Auger Recombination in InAs 1.3-/mu m Quantum-Dot Lasers Investigated Using High Hydrostatic Pressure'. IEEE Journal of Selected Topics in Quantum Electronics, IEEE Journal of Selected Topics in Quantum Electronics 9 (5)

    Abstract

    InAs quantum-dot (QD) lasers were investigated in the temperature range 20-300 K and under hydrostatic pressure in the range of 0-12 kbar at room temperature. The results indicate that Auger recombination is very important in 1.3-mum QD lasers at room temperature and it is, therefore, the possible cause of the relatively low characteristic temperature observed, of T-0 = 41 K. In the 980-mn QD lasers where T-0 = 110-130 K, radiative recombination dominates. The laser emission photon energy E-las increases linearly with pressure p at 10.1 and 8.3 meV/kbar for 980 nm and 1.3-mum QD lasers, respectively. For the 980-mn QD lasers the threshold current increases with pressure at a rate proportional to the square of the photon energy E-las(2). However, la the threshold current of the 1.3-mum QD laser decreases. by 26% over a 12-kbar pressure range. This demonstrates the presence of a nonradiative recombination contribution to the threshold current, which decreases with increasing pressure. The authors show that this nonradiative contribution is Auger recombination. The results are discussed in the framework of a theoretical model based on the electronic structure and radiative recombination calculations carried out using an 8 x 8 k(.)p Hamiltonian.

  • Marko IP, Andreev AD, Adams AR, Krebs R, Reithmaier JP, Forchel A. (2003) 'Importance of Auger recombination in InAs 1.3 mu m quantum dot lasers'. ELECTRONICS LETTERS, 39 (1), pp. 58-59.
  • Marko IP, Andreev AD, Adams AR, Krebs R, Reithmaier JP, Forchel A. (2003) 'Auger recombination in 1.3-μm InAs/GaInAs quantum dot lasers studied using high pressure'. Conference on Lasers and Electro-Optics Europe - Technical Digest, , pp. 175-175.

    Abstract

    The Auger recombination in 1.3μm InAs/GalnAs quantum dot lasers were investigated. To analyse the experimental results, theoretical model was used which includes strain, piezoelectric field and electronic structure calculated in the QDs of truncated pyramid shape. It was found that the radiative current increases with pressure, but the Auger recombination current decreases with pressure and is the dominant recombination path at room temperature in 1.3μm QD lasers. © 2003 IEEE.

Conference papers

  • Sweeney SJ, Marko IP, Jin SR, Hild K, Batool Z, Ludewig P, Natterman L, Bushell Z, Stolz W, Volz K, Broderick CA, Usman M, Harnedy PE, O'Reilly EP, Butkute R, Pacebutas V, Geizutis A, Krotkus A. (2014) 'Electrically injected GaAsBi Quantum Well Lasers'. IEEE COMPUTER SOC 2014 24TH IEEE INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE (ISLC 2014), Palma de Mallorca, SPAIN: 24th IEEE International Semiconductor Laser Conference (ISLC), pp. 80-81.

    Abstract

    GaAsBi QWs have the potential to remove inherent recombination losses thereby increasing the efficiency and reducing the temperature sensitivity of near-infrared telecommunications lasers. GaAsBi QW lasers are reported and prospects for 1550nm operation are discussed.

  • Adams AR, Marko I, Mukherjee J, Sweeney S, Gocalinska A, Pelucchi E, Corbett B. (2014) 'Semiconductor quantum well lasers with a temperature insensitive threshold current'. Conference Digest - IEEE International Semiconductor Laser Conference, , pp. 82-83.
  • Ikyo BA, Marko IP, Hild K, Adams AR, Sweeney SJ, Arafin S, Amann M-C. (2013) 'The effect of hole leakage and auger recombination on the temperature sensitivity of GaInAsSb/GaSb mid-infrared lasers'. IEEE Lasers and Electro-Optics Europe (CLEO EUROPE/IQEC), 2013 Conference on and International Quantum Electronics Conference, Munich: Lasers and Electro-Optics Europe (CLEO EUROPE/IQEC), 2013 Conference on and International Quantum Electronics Conference
  • Crutchley BG, Marko IP, Adams AR, Sweeney SJ. (2013) 'Investigating the efficiency limitations of GaN-based emitters'. Optics InfoBase Conference Papers,
  • Hild K, Batool Z, Jin SR, Hossain N, Marko IP, Hosea TJC, Lu X, Tiedje T, Sweeney SJ. (2013) 'Auger Recombination Suppression And Band Alignment In GaAsBi/GaAs Heterostructures'. AMER INST PHYSICS PHYSICS OF SEMICONDUCTORS, Zurich, SWITZERLAND: 31st International Conference on the Physics of Semiconductors (ICPS) 1566, pp. 488-489.

    Abstract

    Using a combination of experimental and theoretical techniques we present the dependence of the bandgap Eg and the spin orbit splitting energy so, with Bi concentration in GaAsBi/GaAs samples. We find that the concentration at which so,> Eg occurs at 9%. Both spectroscopic as well as first device results indicate a type I alignment.

  • Hosea TJC, Chai GMT, Marko IP, Batool Z, Hild K, Jin SR, Hossain N, Sweeney SJ, Petropoulos JP, Zhong Y, Dongmo PB, Zide JMO. (2012) 'InGaBiAs/InP semiconductors for mid-infrared applications: Dependence of bandgap and spin-orbit splitting on temperature and bismuth content'. ICP 2012 - 3rd International Conference on Photonics 2012, Proceedings, , pp. 154-158.

    Abstract

    Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ>E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ(x, T) in InGa BiAs/InP samples for 0≤x≤0.032 by optical spectroscopy. While we find no clear evidence of a decreased dE /dT (≈0.33±0.07meV/K in all samples) we find Δ>E for x>3.3-4.3%. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 IEEE.

  • Lever L, Hu Y, Myronov M, Liu X, Owens N, Gardes FY, Marko IP, Sweeney SJ, Ikonić Z, Leadley DR, Reed GT, Kelsall RW. (2011) 'Strain engineering of the electroabsorption response in Ge/SiGe multiple quantum well heterostructures'. IEEE 8th IEEE International Conference on Group IV Photonics, London, UK: Group IV Photonics, pp. 107-108.

    Abstract

    Many fibre-optic telecommunications systems exploit the spectral `window' at 1310 nm, which corresponds to zero dispersion in standard single-mode fibres (SMFs). In particular, several passive optical network (PON) architectures use 1310 nm for upstream signals,1 and so compact, low-cost and low-power modulators operating at 1310 nm that can be integrated into Si electronic-photonic integrated circuits would be extremely desireable for future fibre-to-the-home (FTTH) applications.

  • Mashanovich GZ, Headley WR, Milosevic MM, Owens N, Teo EJ, Xiong BQ, Yang PY, Nedeljkovic M, Anguita J, Marko I, Hu Y. (2010) 'Waveguides for mid-infrared group IV photonics'. Proceedings of IEEE 7th International Conference on Group IV Photonics, Beijing, China: 7th IEEE GFP, pp. 374-376.

    Abstract

    In this paper we present preliminary work on group IV photonic waveguides that may be suitable for mid-infrared wavelengths. Fabrication and experimental results for two waveguide structures are given.

  • Sayid SA, Marko IP, Sweeney SJ, Poole P. (2010) 'Temperature sensitivity of 1.55μm (100) InAs/InP-based quantum dot lasers'. IEEE Proceedings of 22nd International Conference on Indium Phosphide and Related Materials, Kagawa, Japan: 22nd IPRM, pp. 23-24.

    Abstract

    Semiconductor lasers with quantum dot (QD) based active regions have generated a huge amount of interest for applications including communications networks due to their anticipated superior physical properties due to three dimensional carrier confinement. For example, the threshold current of ideal quantum dots is predicted to be temperature insensitive. We have investigated the operating characteristics of 1.55 μm InAs/InP (100) quantum dot lasers focusing on their carrier recombination characteristics using a combination of low temperature and high pressure measurements. By measuring the intrinsic spontaneous emission from a window fabricated in the n-contact of the devices we have measured the radiative component of the threshold current density, Jrad. We find that Jrad is itself relatively temperature insensitive (Fig. 1). However, the total threshold current density, Jth, increases significantly with temperature leading to a characteristic temperature T0~72 K around 220 K-290 K. From this data it is clear that the devices are dominated by a non-radiative recombination process which accounts for up to 94% of the threshold current at room temperature (Fig. 1).

  • Sayid SA, Marko IP, Cannard PJ, Chen X, Rivers LJ, Lealman IF, Sweeney SJ. (2010) 'Thermal performance of 1.55μm InGaAlAs quantum well buried heterostructure lasers'. IEEE Proceedings of 22nd International Conference on Indium Phosphide and Related Materials, Kagawa, Japan: 22nd IPRM, pp. 265-268.

    Abstract

    We have investigated the threshold current Ith and differential quantum efficiency as the function of temperature in InGaAlAs/InP multiple quantum well (MQWs) buried heterostructure (BH) lasers. We find that the temperature sensitivity of Ith is due to non-radiative recombination which accounts for up to ~80% of Jth at room temperature. Analysis of spontaneous emission emitted from the devices show that the dominant non-radiative recombination process is consistent with Auger recombination. We further show that the above threshold differential internal quantum efficiency, ηi, is ~80% at 20°C remaining stable up to 80°C. In contrast, the internal optical loss, αi, increases from 15 cm-1 at 20°C to 22 cm-1 at 80°C, consistent with inter-valence band absorption (IVBA). This suggests that the decrease in power output at elevated temperatures is associated with both Auger recombination and IVBA.

  • Tan SL, Tan LJJ, Goh YL, Zhang S, Ng JS, David JPR, Marko IP, Allam J, Sweeney SJ, Adams AR. (2010) 'Reduction of dark current and unintentional background doping in InGaAsN photodetectors by ex situ annealing'. SPIE Proceedings of SPIE - Posters Session, Brussels, Belgium: Optical Sensing and Detection 7726

    Abstract

    InGaAsN is a promising material system to enable low-cost GaAs-based detectors to operate in the telecommunication spectrum, despite the problems posed by the low growth temperature required for nitrogen incorporation. We demonstrate that InGaAsN p+-i-n+ structures with nominal In and N fraction of 10% and 3.8%, grown by molecular beam epitaxy (MBE) under non-optimal growth conditions, can be optimized by post growth thermal annealing to match the performance of optimally grown structures. We report the findings of an annealing study by comparing the photoluminescence spectra, dark current and background concentration of the as-grown and annealed samples. The dark current of the optimally annealed sample is approximately 2 μA/cm2 at an electric field of 100 kV/cm, and is the lowest reported to date for InGaAsN photodetectors with a cut-off wavelength of 1.3 μm. Evidence of lower unintentional background concentration after annealing at a sufficiently high temperature, is also presented.

  • Ikyo BA, Marko IP, Adams AR, Sweeney SJ, Canedy CL, Vurgaftman I, Kim CS, Kim M, Bewley WW, Meyer JR. (2010) 'Temperature sensitivity of mid-infrared type II "W" interband cascade lasers (ICL) emitting at 4.1μm at room temperature'. IEEE 22nd IEEE International Semi-conductor Laser Conference, Kyoto, Japan: ISLC 2010, pp. 41-42.

    Abstract

    The thermal properties of 5-stage “W” Interband-Cascade Lasers emitting at 4.1μm at RT are investigated. It is shown that inter-valence band absorption coupled with non-radiative recombination govern their maximum operating temperature.

  • Crutchley BG, Marko IP, Adams AR, Sweeney SJ. (2010) 'Efficiency limitations of green InGaN LEDs and laser diodes'. 22nd IEEE International Semiconductor Laser Conference, Kyoto, Japan: ISLC 2010, pp. 27-28.
  • Sayid SA, Marko IP, Adams AR, Sweeney SJ, Barrios P, Poole P. (2010) 'Thermal behavior of 1.55 μm (100) InAs/InP-based quantum dot lasers'. IEEE Poceeedings of 22nd International Semiconductor Laser Conference, Kyoto, Japan: ISLC 2010, pp. 75-76.

    Abstract

    Unlike InAs/GaAs quantum dot lasers, in 1.55μm InAs/InP devices, non-radiative recombination dominates device behavior from very low temperature (~40K) and accounts for ~94% of Jth at room temperature with a To of ~72K from 220K-290K.

  • Ikyo AB, Marko IP, Adams AR, Sweeney SJ, Bachmann A, Kashani-Shirazi K, Amann M-C. (2009) 'Gain peak-cavity mode alignment optimisation in buried tunnel junction mid-infrared GaSb vertical cavity surface emitting lasers using hydrostatic pressure'. INST ENGINEERING TECHNOLOGY-IET IET OPTOELECTRONICS, Cardiff, WALES: Semiconductor and Integrated Optoelectronics Conference (SIOE 2009) 3 (6), pp. 305-309.
  • Marko IP, Ikyo AB, Adams AR, Sweeney SJ, Bachmann A, Kashani-Shirazi K, Amann M-C. (2009) 'Band-structure and gain-cavity tuning of 2.4-μm GaSb buried tunnel junction VCSELs'. Proceedings of European Conference on Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference, Munich, Germany: CLEO Europe - EQEC 2009

    Abstract

    Low-cost, continuous-wave GaSb-based vertical cavity surface emitting lasers (VCSELs) operating at ~ 2.4 mum up to 50degC have been demonstrated recently. In this work we have used high pressure techniques to investigate ways to improve their performance and extend their working temperature range. Since the band-gap and energy of the gain peak (Ep) increase with pressure at 0.126 meV/MPa at constant temperature, when applied to edge emitting lasers (EEL) we can use pressure to determine the radiative and non-radiative recombination processes occurring. In the VCSEL the pressure dependence of the threshold current, is much more complicated. At the higher temperature the decreasing Auger recombination initially dominates. Therefore we predict that either increasing the band gap or increasing the operating wavelength will allow an improved temperature performance of these GaSb-based VCSELs.

  • Marko IP, Adams AR, Sweeney SJ, Teissier R, Baranov AN, Tomic S. (2009) 'Evidence of carrier leakage into the L-valley in InAs-based quantum cascade lasers under high hydrostatic pressure'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Fortaleza, BRAZIL: 13th International Conference on High Pressure Semiconductor Physics (HPSP-13) 246 (3), pp. 512-515.
  • Tan LJJ, Soong WS, Tan SL, Goh YL, Steer MJ, Ng JS, David JPR, Marko IP, Chamings J, Allam J, Sweeney SJ, Adams AR. (2009) 'Dark current mechanisms in InxGa1-xAs 1-yNy'. IEEE IEEE Proceedings of LEOS Annual Meeting Conference, Belek-Antalya, Turkey: LEOS '09, pp. 233-234.

    Abstract

    In order to extend the photo response of GaAs to optical telecommunication wavelengths, In and N can be incorporated into GaAs to yield a perfect lattice match of InxGa1-xAs1-yNy with GaAs with a bandgap that strongly decreases with increasing N composition. The potential usage of such a material as photodetectors and photovoltaic applications has been reported.In this work, we investigate the dark current mechanisms in the InxGa1-xAs1-yNy material.

  • Marko IP, Ikyo AB, Adams AR, Sweeney SJ, Bachmann A, Kashani-Shirazi K, Amann M-C. (2009) 'Band-structure and gain-cavity tuning of 2.4-μm GaSb buried tunnel junction VCSELs'. Optics InfoBase Conference Papers,
  • Adams AR, Marko IP, Sweeney SJ, Teissier R, Baranov AN, Tomic S. (2009) 'The effect of hydrostatic pressure on the operation of quantum cascade lasers'. SPIE-INT SOC OPTICAL ENGINEERING QUANTUM SENSING AND NANOPHOTONIC DEVICES VI, San Jose, CA: Conference on Quantum Sensing and Nanophotonic Devices VI 7222
  • Lealman I, Dosanjh S, Rivers L, O'Brien S, Cannard P, Sweeney SJ, Marko IP, Rushworth S. (2008) 'Reliable 1550nm SI BH lasers fabricated using an improved Ru precursor'. 20th International Conference on Indium Phosphide and Related Materials, Versailles, France: IPRM 2008

    Abstract

    We have fabricated and assessed 1550 nm SIBH FP lasers using a novel Ruthenium precursor for MOVPE. Low temperature analysis revealed no unexpected defects and performance is similar to standard p-n-p-n current blocking devices. Accelerated aging at 85degC indicates no significant degradation after 5,700 hours on test.

  • Marko IP, Adams AR, Sweeney SJ, Teissier R, Baranov AN, Tomic S. (2008) 'Gamma-L scattering in InAs-based quantum cascade lasers studied using high hydrostatic pressure'. IEEE 2008 IEEE 21ST INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE, Sorrento, ITALY: IEEE 21st International Semiconductor Laser Conference, pp. 47-48.
  • Crowley MT, Marko IP, Masse NF, Andreev AD, Sweeney SJ, O'Reilly EP, Adams AR. (2008) 'The importance of recombination via excited states in InAs/GaAs 1.3μm quantum dot lasers'. IEEE IEEE Proceedings of 21st International Semiconductor Laser Conference, Sorento, Italy: 21st ISLC 2008, pp. 117-118.

    Abstract

    The optical matrix element for excited-states is significantly weaker than the ground-state leading to thermally stable radiative recombination. This is not so for non-radiative Auger recombination, causing a sharp increase in threshold current with temperature.

  • Sweeney SJ, Hild K, Marko IP, Yu S-Q, Johnson SR, Zhang Y-H. (2008) 'Thermal characteristics of 1.3 mu m GaAsSb/GaAs-based Edge- and Surface-emitting Lasers'. IEEE 2008 IEEE 21ST INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE, Sorrento, ITALY: IEEE 21st International Semiconductor Laser Conference, pp. 83-84.
  • Marko IP, Masse NF, Sweeney SJ, Adams AR, Hatori N, Sugawara M. (2007) 'Recombination, transport and loss mechanisms in p-doped InAs/GaAs quantum dots'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 837-838.
  • Marko IP, Adams AR, Sweeney SJ, Masse NF, Krebs R, Reithmaier JP, Forchel A, Mowbray DJ, Skolnick MS, Liu HY, Groom KM, Hatori N, Sugawara M. (2007) 'Band gap dependence of the recombination processes in InAs/GaAs quantum dots studied using hydrostatic pressure'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Barcelona, SPAIN: 12th International Conference on High Pressure Semiconductor Physics (HPSP-12) 244 (1), pp. 82-86.
  • Marko IP, Adams AR, Sweeney SJ, Whitbread ND, Ward AJ, Asplin B, Robbins DJ. (2007) 'The influence of carrier density non-pinning on the output power of 1.55 μm lasers at high temperature'. IEEE Lasers and Electro-Optics, 2007 and the International Quantum Electronics Conference, Munich, Germany: CLEOE-IQEC 2007, pp. 1-1.
  • Hild K, Sweeney SJ, Marko IP, Jin SR, Johnson SR, Chaparro SA, Yu S, Zhang Y-H. (2007) 'Temperature and pressure dependence of carrier recombination processes in GaAsSb/GaAs quantum well lasers'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Barcelona, SPAIN: 12th International Conference on High Pressure Semiconductor Physics (HPSP-12) 244 (1), pp. 197-202.
  • Massé NF, Sweeney SJ, Marko IP, Andreev AD, Adams AR, Hatori N, Sugawara M. (2006) 'Intrinsic limitations of p-doped and undoped 1.3 μm InAs/GaAs quantum dot lasers'. IEEE 20th IEEE International Semi-conductor Laser Conference - Conference Digest, Hawaii, USA: ISLC 2006, pp. 143-144.

    Abstract

    The temperature dependencies of the recombination and gain processes reveal intrinsic limitations on the performances of quantum dot lasers. Controlling the transport of the carriers using the inhomogeneous broadening makes temperature stable threshold current possible

  • Marko I, Masse N, Sweeney S, Adams A, Sellers I, Mowbray D, Skolnick M, Liu H, Groom K. (2005) 'Effect of gain saturation and nonradiative recombination on the thermal characteristics of InAs/GaAs 1.3 mu m quantum dot lasers'. IEEE The 18th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2005. (LEOS 2005), Sydney, NSW, Australia: 18th Annual Meeting of the IEEE Lasers and Electro-Optics Society, pp. 401-402.

    Abstract

    Gain saturation increases the radiative component, J(rad), of the threshold current density, J(th), and its contribution to the thermal sensitivity of J(th) in short cavity or low QD density devices. However, the main cause of their thermal sensitivity is a strong non-radiative recombination.

  • Marko I, Adams AR, Sweeney S, Mowbray D, Skolnick M, Liu H, Groom K. (2005) 'Recombination and loss mechanisms in low-threshold InAs-GaAs 1.3-mu m quantum-dot lasers'. IEEE IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, Matsue, JAPAN: 19th IEEE International Semiconductor Laser Conference 11 (5), pp. 1041-1047.

    Abstract

    We show that even in quantum-dot (QD) lasers with very low threshold current densities (J(th) = 40-50 A/cm(2) at 300 K), the temperature sensitivity of the threshold current arises from nonradiative recombination that comprises similar to 60% to 70% of J(th) at 300 K, whereas the radiative part of J(th) is almost temperature insensitive. The influence of the nonradiative recombination mechanism decreases with increasing hydrostatic pressure and increasing band gap, which leads to a decrease of the threshold current. We also studied, for the first time, the band gap dependence of the radiative part Of Jth, which in contrast increases strongly with increasing band gap. These results suggest that Auger recombination is an important intrinsic recombination mechanism for 1.3-mu m lasers, even in a very low threshold QD device, and that it is responsible for the temperature sensitivity of the threshold current.

  • Marko IP, Andreev AD, Sweeney SJ, Adams AR, Krebs R, Deubert S, Reithmaier JP, Forchel A. (2005) 'The influence of auger processes on recombination in long-wavelength InAs/GaAs quantum dots'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Flagstaff, AZ: 27th International Conference on the Physics of Semiconductors (ICPS-27) 772, pp. 681-682.
  • Masse N, Marko I, Sweeney S, Adams AR, Hatori N, Sugarawa M. (2005) 'The influence of p-doping on the temperature sensitivity of 1.3 mu m quantum dot lasers'. IEEE 2005 IEEE LEOS Annual Meeting Conference Proceedings (LEOS), Sydney, Australia: 2005 IEEE LEOS Annual Meeting Conference (LEOS), pp. 603-604.

    Abstract

    We find that non-radiative recombination plays an important role in p-doped quantum-dot lasers. Along with carrier thermalisation effects, this is responsible for the temperature insensitive operation as observed around room temperature in these lasers.

  • Marko IP, Sweeney SJ, Adams AR, Jin SR, Murdin BN, Schwertberger R, Somers A, Reithmaier JP, Forchel A. (2004) 'Recombination mechanisms in InAs/InP quantum dash lasers studied using high hydrostatic pressure'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC RESEARCH, Berkeley, CA: 11th International Conference on High-Pressure Semiconductor Physics (HPSP-11) 241 (14), pp. 3427-3431.
  • Marko IP, Adams AR, Sweeney SJ, Jin SR, Murdin BN, Schwertberger R, Somers A, Reithmaier JP, Forchel A. (2004) 'Experimental investigations into the thermal properties of 1.5-1.8-mu m InAs/InP quantum dash lasers'. IEEE 2004 IEEE 19TH INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE, CONFERENCE DIGEST, Matsue, JAPAN: 19th IEEE International Semiconductor Laser Conference, pp. 61-62.
  • Marko I, Adams AR, Sweeney S, Sellers I, Mowbray D, Skolnick M, Liu H, Groom K. (2004) 'Recombination and loss mechanisms in low-threshold InAs/GaAs 1.3 mu m quantum dot lasers'. 2004 IEEE 19TH INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE, CONFERENCE DIGEST, Matsue, JAPAN: 19th IEEE International Semiconductor Laser Conference, pp. 57-58.

    Abstract

    We show that even in quantum dot lasers with very low threshold current density (Jth=740-50 A/cm(2) at 300 K) the temperature sensitivity of the threshold current arises from nonradiative recombination which comprises similar to60-70% of Jth at 300 K.

  • Fehse R, Marko I, Adams AR. (2003) 'Long wavelength lasers on GaAs substrates'. IEE-INST ELEC ENG IEE PROCEEDINGS-CIRCUITS DEVICES AND SYSTEMS, MUMBAI, INDIA: 6th International Conference on Optoelectronics, Fibre Optics and Photonics 150 (6), pp. 521-528.
  • Marko IP, Andreev AD, Adams AR, Krebs R, Reithmaier JP, Forchel A. (2003) 'High-pressure studies of the recombination processes, threshold currents, and lasing wavelengths in InAs/GaInAs quantum dot lasers'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC RESEARCH, UNIV SURREY, GUILDFORD, ENGLAND: 10th International Conference on High Pressures in Semiconductor Physics (HPSP-X) 235 (2), pp. 407-411.

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