Jeremy Allam

Professor Jeremy Allam


Professor of Ultrafast Optoelectronics
+44 (0)1483 686799
13 ATI 01

Biography

University roles and responsibilities

  • FHEQ Level 6/7 Year Coordinator (Final Year)

    Research

    Research interests

    My teaching

    My publications

    Publications

    Till Buchacher, M Rokosz, Robert Dorey, Jeremy Allam, A Gregory (2017)Electrocaloric induced retarded ferroelectric switching, In: Applied Physics Letters110(2) AIP Publishing

    Ferroelectric switching in bulk materials, at modest electric fields, is a relatively fast process, occurring on time scales of microseconds and less. A secondary retarded switching phenomenon also occurs on time scales of seconds and has previously been attributed to defect induced elevated energy barriers between polarisation states. As ferroelectric switching is a thermally activated process the barrier heights are also affected by temperature which is not constant in ferroelectric materials due to the electrocaloric effect. Here an additional EC induced retardation mechanism is proposed whereby EC induced temperature changes repeatedly temporarily prevent further FE switching during cooling cycles.

    K L Litvinenko, B N Murdin, J Allam, C R Pidgeon, T Zhang, J J Harris, L F Cohen, D A Eustace, D W McComb (2006)Spin Lifetime in InAs Epitaxial Layers Grown on GaAs, In: Physical Review B74(7)

    We report investigation of the spin relaxation in InAs films grown on GaAs at a temperature range from 77 K to 290 K. InAs is known to have a surface accumulation layer and the depth profile of the concentration and mobility is strongly nonuniform. We have correlated the spin relaxation with a multilayer analysis of the transport properties and find that the surface and the interface with the GaAs substrate both have subpicosecond lifetimes (due to the high carrier concentration), whereas the central semiconducting layer has a lifetime of an order of 10 ps. Even for the thickest film studied (1 mu m), the semiconducting layer only carried 30% of the total current (with 10% through the interface layer and 60% through the surface accumulation layer). Designs for spintronic devices that utilize InAs, which is attractive due to its narrow gap and strong Rashba effect, will need to include strategies for minimizing the effects of the surface.

    Jose Anguita, David Cox, Muhammad Ahmad, YY Tan, Jeremy Allam, S Silva (2013)Highly transmissive carbon nanotube forests grown at low substrate temperature, In: Advanced Functional Materials23(44)pp. 5502-5509 Wiley

    Despite the "darker than black" association attributed to carbon nanotube forests, here is shown that it is also possible to grow these structures, over heat-sensitive substrates, featuring highly transmissive characteristics from the UV to infrared wavelengths, for forest heights as high as 20 μm. The optical transmission is interpreted in terms of light propagation along channels that are self-generated by localized bundling of tubes, acting as waveguides. A good correlation is shown between the distribution of diameter sizes of these sub-wavelength voids and the transmission spectrum of the forests. For the shorter visible and near-UV wavelengths, this model shows that light propagates by channeling along individual vertical voids in the forests, which elucidates the origin for the widely-reported near-zero reflectance values observed in forests. For the longer infrared wavelengths, the mode spreads over many nanotubes and voids, and propagates along a "homogeneous effective medium". The strong absorption of the forest at the shorter wavelengths is correlated in terms of the stronger attenuation inside a waveguide cavity, according to the λ attenuation dependency of standard waveguide theory. The realization of this material can lead to novel avenues in new optoelectronic device design, where the carbon nanotube forests can be used as highly conducting "scaffolds" for optically active materials, whilst also allowing light to penetrate to significant depths into the structure, in excess of 20 μm, enabling optical functionality. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    I Galbraith, R Chari, S Pellegrini, P J Phillips, C J Dent, A F van der Meer, D G Clarke, A K Kar, G S Buller, C R Pidgeon, B N Murdin, J Allam, G Strasser (2005)Excitonic Signatures in the Photoluminescence and Terahertz Absorption of a GaAs/AlxGa1-xAs Multiple Quantum Well, In: Physical Review B71(7)

    Measurements of the THz absorption and the time-resolved photoluminescence have been performed on the same GaAs quantum well sample. The strength of the absorption at the internal 1s-2p exciton transition frequency is used as a measure of the density of excitons in the sample. When the interband pump laser is resonant with the Is exciton frequency, induced absorption at the 1s-2p frequency is clearly seen. If the same density of carriers is created pumping in the continuum, no significant 1s-2p absorption is seen in a time window of 450 ps. Complementary time-resolved photoluminescence experiments, detecting the emission at the exciton energy under the same pump conditions, show the PL intensity in resonant and nonresonant cases to be similar. The counter-intuitive existence of luminescence at the exciton energy simultaneously with the absence of the 1s-2p absorption is consistent with the recent theoretical predictions of Kira et al., Phys. Rev. Lett. 81, 3263 (1998).

    P Murzyn, C R Pidgeon, P J Phillips, M Merrick, K L Litvinenko, J Allam, B N Murdin, T Ashley, J H Jefferson, A Miller, L F Cohen (2003)Suppression of D'yakonov-Perel Spin Relaxation in InAs and InSb by n-Type Doping at 300 K, In: Applied Physics Letters83(25)

    We have made direct pump-probe measurements of spin lifetimes in intrinsic and degenerate n-InAs at 300 K. In particular, we measure remarkably long spin lifetimes (tau(s)similar to1.6 ns) for near-degenerate epilayers of n-InAs. For intrinsic material, we determine tau(s)similar to20 ps, in agreement with other workers. There are two main models that have been invoked for describing spin relaxation in narrow-gap semiconductors: the D'yakonov-Perel (DP) model and the Elliott-Yafet (EY) model. For intrinsic material, the DP model is believed to dominate in III-V materials above 77 K, in agreement with our results. We show that in the presence of strong n-type doping, the DP relaxation is suppressed both by the degeneracy condition and by electron-electron scattering, and that the EY model then dominates for the n-type material. We show that this same process is also responsible for a hitherto unexplained lengthening of tau(s) with n-type doping in our earlier measurements of n-InSb.

    KL Litvinenko, L Nikzad, CR Pidgeon, J Allam, LF Cohen, T Ashley, M Emeny, W Zawadzki, BN Murdin (2008)Temperature dependence of the electron Lande g factor in InSb and GaAs, In: PHYSICAL REVIEW B77(3)ARTN 0pp. ?-? AMER PHYSICAL SOC
    JS Ng, SL Tan, YL Goh, CH Tan, JPR David, J Allam, SJ Sweeney, AR Adams (2010)InGaAsN as absorber in APDs for 1.3 micron wavelength applicationspp. 187-190

    Two issues with using InGaAsN as absorber in avalanche photodiodes (APDs) for 1310nm wavelength applications are addressed here. Firstly, we demonstrated InGaAsN p-i-n diodes with stable photoresponse around 1310nm but reverse leakage current density slightly above the acceptable limit of ~0.2mA/cm2 at 150kV/cm. We also investigated whether or not InGaAsN as absorber is compatible with Al0.8Ga0.2As (the proposed avalanche material in our separate-absorption-multiplication APD design) in terms of the relationship between α and β in InGaAsN. Our observations suggest α ~ β in InGaAsN, making it compatible with Al0.8Ga0.2As.

    Jose Anguita, Muhammad Ahmad, S Haq, Jeremy Allam, S Silva (2016)Ultra-broadband light trapping using nanotextured decoupled graphene multilayers, In: Science Advances2(2)e1501238 American Association for the Advancement of Science

    The ability to engineer a thin two-dimensional surface for light trapping across an ultra-broad spectral range is central for an increasing number of applications including energy, optoelectronics, and spectroscopy. Although broadband light trapping has been obtained in tall structures of carbon nanotubes with millimeter-tall dimensions, obtaining such broadband light–trapping behavior from nanometer-scale absorbers remains elusive. We report a method for trapping the optical field coincident with few-layer decoupled graphene using field localization within a disordered distribution of subwavelength-sized nanotexturing metal particles. We show that the combination of the broadband light–coupling effect from the disordered nanotexture combined with the natural thinness and remarkably high and wavelength-independent absorption of graphene results in an ultrathin (15 nm thin) yet ultra-broadband blackbody absorber, featuring 99% absorption spanning from the mid-infrared to the ultraviolet. We demonstrate the utility of our approach to produce the blackbody absorber on delicate opto-microelectromechanical infrared emitters, using a low-temperature, noncontact fabrication method, which is also large-area compatible. This development may pave a way to new fabrication methodologies for optical devices requiring light management at the nanoscale.

    JS Ng, WM Soong, MJ Steer, M Hopkinson, JPR David, J Chamings, AR Adams, SJ Sweeney, J Allam (2007)GaInNAs lattice-matched to GaAs for photodiodes, In: Conference Proceedings - International Conference on Indium Phosphide and Related Materialspp. 347-349

    We present optical and electrical characterization data obtained from bulk GaInNAs (lattice-matched to GaAs) diodes with varying GaInNAs composition. Good lattice-matching to GaAs, low reverse dark current and long wavelength absorption were achieved simultaneously, without the aid of post-growth annealing and use of antimony during the growth. © 2007 IEEE.

    J Allam, R Sutton, M Sjjad, K Litvinenko, S Siddique, Z Wang, Q-H Yang, T Brwon, W Loh (2010)Reaction, diffusion and dissociation of excitons on carbon nanotubes, In: OSA Technical Digest (CD)

    We study exciton reactions on carbon nanotubes in the regime of many, few and one exciton per nanotube, and demonstrate classic 1-D reaction-diffusion behaviour. Dissociation occurs when exciton spacing is less than the exciton length.

    WM Soong, JS Ng, MJ Steer, M Hopkinson, JPR David, J Chamings, SJ Sweeney, AR Adams, J Allam (2008)Dark current mechanisms in bulk GaInNAs photodiodes, In: Proccedings of 20th International Conference on Indium Phosphide and Related Materials

    We have grown a series of bulk GaInNAs p-i-n diodes and identified some of the dark current mechanisms present in our devices. With a nitrogen composition of ~4 %, the band gap can be reduced to 0.94 eV. We also demonstrate that low dark current density is achievable without compromising the absorption and hence quantum efficiency up to 1.4 mum.

    S Tan, CJ Hunter, S Zhang, LJJ Tan, YL Goh, JS Ng, JPR David, Igor Marko, Stephen Sweeney, Alfred Adams, Jeremy Allam (2012)Improved optoelectronic properties of rapid thermally annealed dilute nitride GaInNAs photodetectors, In: Journal of Electronic Materials41(12)pp. 3393-3401 IEEE

    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.

    SL Tan, LJJ Tan, YL Goh, S Zhang, JS Ng, JPR David, IP Marko, J Allam, SJ Sweeney, AR Adams (2010)Reduction of dark current and unintentional background doping in InGaAsN photodetectors by ex situ annealing, In: Proceedings of SPIE - Posters Session7726

    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.

    C O'Rourke, J Allam, D Baxter, K Boehringer, A Klaedtke, J Hamm, O Hess (2006)Coherent generation and control of long-lived ultra-short transients in a semiconductor laser - art. no. 61840M, In: Semiconductor Lasers and Laser Dynamics II618461840Mpp. M1840-M1840 SPIE-INT SOC OPTICAL ENGINEERING

    We investigate the evolution of short-duration pulses injected into laser diodes biased above threshold with the use of spectrally and temporally resolved experimental and numerical methods. We show that stable transients may be formed as a result of spatially re-distributing the cavity energy. By controlling the phase of injected pulses with respect to the diode cavity radiation we show through simulation that it is possible to directly generate and control stable streams of pulses.

    KL Litvinenko, BN Murdin, SK Clowes, L Nikzad, J Allam, CR Pidgeon, W Branford, LF Cohen, T Ashley, L Buckle (2008)Density and well-width dependence of the spin relaxation in n-InSb/AlInSb quantum wells, In: NARROW GAP SEMICONDUCTORS 2007119pp. 19-21
    KL Litvinenko, L Nikzad, J Allam, BN Murdin, CR Pidgeon, JJ Harris, LF Cohen (2007)Spin dynamics in narrow-gap semiconductor epitaxial layers, In: JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM20(6)pp. 461-465
    S Bhattacharyya, SJ Henley, E Mendoza, L Gomez-Rojas, J Allam, SRP Silva (2006)Resonant tunnelling and fast switching in amorphous-carbon quantum-well structures, In: NATURE MATERIALS5(1)pp. 19-22 NATURE PUBLISHING GROUP
    K. L. Litvinenko, L. Nikzad, C. R. Pidgeon, J. Allam, L. F. Cohen, T. Ashley, M. Emeny, W. Zawadzki, B. N. Murdin (2008)Temperature dependence of the electron Landé g factor in InSb and GaAs, In: Physical Review B77(033204)

    We report Larmor precession in bulk InSb observed in the time domain from 77 to 300 K. The optically oriented polarization precesses coherently even at 300 K. The inferred Zeeman spin splitting is strongly nonparabolic, and the electron g factor (g*) is in good agreement with k·p theory (provided we take only the dilational contribution to the change in energy gap with temperature). We also show here that correct application of the 14-band k·p model agrees with apparently anomalous trends previously reported for GaAs and confirm that the most widely quoted formula for g* in GaAs is incomplete.

    R. Chari, I. Galbraith, J. Phillips, S. Pellegrini, C. J. Dent, A. K. Kar, G. S. Buller, C. R. Pidgeon, D. G. Clarke, B. N. Murdin, J. Allam, A. F. G. van der Meer, G. Strasser (2003)Excitonic signatures in photoluminescence and terahertz absorption

    By measuring THz absorption and time-resolved photoluminescence on the same GaAs quantum well sample we confirm the recent prediction of Kira that PL at the exciton frequency does not require a population of bound excitons.

    J Allam, R Sutton, MT Sajjad, K Litvinenko, Z Wang, S Siddique, QH Yang, T Brown, W Loh (2010)Reaction, diffusion and dissociation of excitons on carbon nanotubes, In: Optics InfoBase Conference Papers

    Photoexcitation of carbon nanotubes generates excitons which decay by exciton-exciton annihilation at sufficient density. We examine this decay under conditions of one, few and many excitons per nanotube. A classic 1D reaction-diffusion behaviour is observed, with decay limited by diffusion for t>3ps and by reaction for t

    I. Galbraith, R. Chari, S. Pellegrini, P. J. Phillips, C. J. Dent, A. F. G. van der Meer, D. G. Clarke, A. K. Kar, G. S. Buller, C. R. Pidgeon, B. N. Murdin, J. Allam, G. Strasser (2005)Excitonic signatures in the photoluminescence and terahertz absorption of a GaAs/AlxGa1–xAs multiple quantum well, In: Physical Review B71(073302)

    Measurements of the THz absorption and the time-resolved photoluminescence have been performed on the same GaAs quantum well sample. The strength of the absorption at the internal 1s-2p exciton transition frequency is used as a measure of the density of excitons in the sample. When the interband pump laser is resonant with the 1s exciton frequency, induced absorption at the s-2p frequency is clearly seen. If the same density of carriers is created pumping in the continuum, no significant 1s-2p absorption is seen in a time window of 450 ps. Complementary time-resolved photoluminescence experiments, detecting the emission at the exciton energy under the same pump conditions, show the PL intensity in resonant and nonresonant cases to be similar. The counter-intuitive existence of luminescence at the exciton energy simultaneously with the absence of the s-2p absorption is consistent with the recent theoretical predictions of Kira et al., Phys. Rev. Lett. 81, 3263 (1998).

    J Roither, S Pichler, M V Kovalenko, W Heiss, P Feychuk, O Panchuck, J Allam, B N Murdin (2006)Two- and One-Dimensional Light Propagations and Gain in Layer-by-Layer-Deposited Colloidal Nanocrystal Waveguides, In: Applied Physics Letters89(11)

    Optical waveguides containing high percentages of colloidal nanocrystals have been fabricated by layer-by-layer deposition on planar and patterned glass substrates. The two- and one-dimensional waveguidings in these structures are demonstrated by propagation loss experiments. The experimental results obtained for various film thicknesses and widths of the waveguide stripes together with simulations of the light propagation indicate that the losses are dominated by surface roughness. The variable stripe length method is used to determine the optical gain of 230 cm(-1) from the amplified spontaneous emission. This high value makes the authors' waveguide structures very promising for applications in amplifiers and lasers with reduced threshold powers.

    K L Litvinenko, L Nikzad, J Allam, B N Murdin, C R Pidgeon, J J Harris, T Zhang, L F Cohen (2007)Spin Lifetime in High Quality InSb Epitaxial Layers Grown on GaAs, In: Journal of Applied Physics101(8)

    The spin relaxation in undoped InSb films grown on GaAs has been investigated in the temperature range from 77 to 290 K. Two distinct lifetime values have been extracted, 1 and 2.5 ps, dependent on film thickness. Comparison of this data with a multilayer transport analysis of the films suggests that the longer time (similar to 2.5 ps at 290 K) is associated with the central intrinsic region of the film, while the shorter time (similar to 1 ps) is related to the highly dislocated accumulation region at the film-substrate interface. Whereas previous work on InAs films grown on GaAs showed that the native surface defect resulted in an additional charge accumulation layer with high conductivity but very short spin lifetime, in InSb layers the surface states introduce a depletion region. We infer that InSb could be a more attractive candidate for spintronic applications than InAs.

    B. N. Murdin, K. Litvinenko, J. Allam, C. R. Pidgeon, M. Bird, K. Morrison, T. Zhang, S. K. Clowes, W. R. Branford, J. Harris, L. F. Cohen (2005)Temperature and doping dependence of spin relaxation in n-InAs, In: Physical Review B72(085346)

    We have used time-resolved spectroscopy to measure the relaxation of spin polarizations in the narrow gap semiconductor material n-InAs as a function of temperature, doping, and pump wavelength. The results are consistent with the D'Yakonov-Perel mechanism for temperatures between 77 and 300 K. However, the data suggest that electron-electron scattering should be taken into account in determining the dependence of the spin lifetime on the carrier concentration in the range 5.2×1016–8.8×1017 cm–3. For a sample with doping of 1.22×1017 cm–3 the spin lifetime was 24 ps at room temperature. By applying a magnetic field in the sample plane we also observed coherent precession of the spins in the time domain, with a g>/i> factor g*=–13, also at room temperature.

    J. Roither, S. Pichler, M. V. Kovalenko, W. Heiss, P. Feychuk, O. Panchuk, J. Allam, B. N. Murdin (2006)Two- and one-dimensional light propagations and gain in layer-by-layer-deposited colloidal nanocrystal waveguides, In: Applied Physics Letters111120(2006)

    Optical waveguides containing high percentages of colloidal nanocrystals have been fabricated by layer-by-layer deposition on planar and patterned glass substrates. The two- and one-dimensional waveguidings in these structures are demonstrated by propagation loss experiments. The experimental results obtained for various film thicknesses and widths of the waveguide stripes together with simulations of the light propagation indicate that the losses are dominated by surface roughness. The variable stripe length method is used to determine the optical gain of 230 cm–1 from the amplified spontaneous emission. This high value makes the authors' waveguide structures very promising for applications in amplifiers and lasers with reduced threshold powers.

    K. L. Litvinenko, B. N. Murdin, J. Allam, C. R. Pidgeon, M. Bird, K. Morris, W. Branford, S. K. Clowes, L. F. Cohen, T. Ashley, L. Buckle (2006)Spin relaxation in n-InSb/AlInSb quantum wells, In: New Journal of Physics8(4)

    We have used time resolved spectroscopy to measure the relaxation of spin polarization in InSb/AlInSb quantum wells (QWs) as a function of temperature and mobility. The results are consistent with the D'yakonov–Perel (DP) mechanism for high mobility samples over the temperature range from 50 to 300 K. For low mobility samples at high temperature the Elliott–Yafet and DP mechanisms become comparable. We show that the mobility can in certain circumstances determine which mechanism is dominant, and that above 1 m2 V-1 s-1 in 20 nm wide InSb QWs it is the DP mechanism. We also give a criterion for the maximum spin lifetime in terms of mobility and temperature, and show that for our 20 nm wide QWs this corresponds to 0.5 ps at 300 K and mobility 1 m2 V-1 s-1.

    K. L. Litvinenko, B. N. Murdin, J. Allam, C. R. Pidgeon, T. Zhang, J. J. Harris, L. F. Cohen, D. A. Eustace, D. W. McComb (2006)Spin lifetime in InAs epitaxial layers grown on GaAs, In: Physical Review B74(075331)

    We report investigation of the spin relaxation in InAs films grown on GaAs at a temperature range from 77 K to 290 K. InAs is known to have a surface accumulation layer and the depth profile of the concentration and mobility is strongly nonuniform. We have correlated the spin relaxation with a multilayer analysis of the transport properties and find that the surface and the interface with the GaAs substrate both have subpicosecond lifetimes (due to the high carrier concentration), whereas the central semiconducting layer has a lifetime of an order of 10 ps. Even for the thickest film studied (1 micro-m, the semiconducting layer only carried 30% of the total current (with 10% through the interface layer and 60% through the surface accumulation layer). Designs for spintronic devices that utilize InAs, which is attractive due to its narrow gap and strong Rashba effect, will need to include strategies for minimizing the effects of the surface.

    P. Murzyn, C. R. Pidgeon, P. J. Phillips, M. Merrick, K. L. Litvinenko, J. Allam, B. N. Murdin, T. Ashley, J. H. Jefferson, A. Miller, L. F. Cohen (2005)Erratum: "Suppression of D'yakonov-Perel spin relaxation in InAs and InSb by n-type doping at 300 K" [Appl. Phys. Lett. 83, 5220 (2003)], In: Applied Physics Letters129901(2005)
    C O'Rourke, J Allam, K Boehringer, A Klaedtke, J Hamm, O Hess (2005)Coherent interactions and long term evolution of ultrafast transients in a semiconductor laser, In: 2005 IEEE LEOS Annual Meeting Conference Proceedings (LEOS)pp. 823-824
    SL Tan, WM Soong, JE Green, MJ Steer, S Zhang, LJJ Tan, JS Ng, IP Marko, SJ Sweeney, AR Adams, J Allam, JPR David (2013)Experimental evaluation of impact ionization in dilute nitride GaInNAs diodes, In: APPLIED PHYSICS LETTERS103(10)ARTN 1pp. ?-? AMER INST PHYSICS
    K. L. Litvinenko, L. Nikzad, J. Allam, B. N. Murdin, C. R. Pidgeon, J. J. Harris, T. Zhang, L. F. Cohen (2007)Spin lifetime in high quality InSb epitaxial layers grown on GaAs, In: Journal of Applied Physics083105(2007)

    The spin relaxation in undoped InSb films grown on GaAs has been investigated in the temperature range from 77 to 290 K. Two distinct lifetime values have been extracted, 1 and 2.5 ps, dependent on film thickness. Comparison of this data with a multilayer transport analysis of the films suggests that the longer time (~2.5 ps at 290 K) is associated with the central intrinsic region of the film, while the shorter time (~1 ps) is related to the highly dislocated accumulation region at the film-substrate interface. Whereas previous work on InAs films grown on GaAs showed that the native surface defect resulted in an additional charge accumulation layer with high conductivity but very short spin lifetime, in InSb layers the surface states introduce a depletion region. We infer that InSb could be a more attractive candidate for spintronic applications than InAs.

    J Allam, MT Sajjad, R Sutton, K Litvinenko, Z Wang, S Siddique, Q-H Yang, WH Loh, T Brown (2013)Measurement of a reaction-diffusion crossover in exciton-exciton recombination inside carbon nanotubes using femtosecond optical absorption, In: Physical Review Letters American Physical Society

    Exciton-exciton recombination in isolated semiconducting single-walled carbon nanotubes was studied using femtosecond transient absorption. Under sufficient excitation to saturate the optical absorption, we observed an abrupt transition between reaction- and diffusion- limited kinetics, arising from reactions between incoherent localized excitons with a finite probability of ~ 0.2 per encounter. This represents the first experimental observation of a crossover between classical and critical kinetics in a 1D coalescing random walk, which is a paradigm for the study of non- equilibrium systems.

    SL Tan, S Zhang, WM Soong, YL Goh, LJJ Tan, JS Ng, JPR David, IP Marko, AR Adams, SJ Sweeney, J Allam (2011)GaInNAsSb/GaAs Photodiodes for Long-Wavelength Applications, In: IEEE ELECTRON DEVICE LETTERS32(7)pp. 919-921 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
    B N Murdin, K Litvinenko, J Allam, C R Pidgeon, M Bird, K Morrison, T Zhang, S K Clowes, W R Branford, J Harris, L F Cohen (2005)Temperature and Doping Dependence of Spin Relaxation in n-InAs, In: Physical Review B72(8)

    We have used time-resolved spectroscopy to measure the relaxation of spin polarizations in the narrow gap semiconductor material n-InAs as a function of temperature, doping, and pump wavelength. The results are consistent with the D'Yakonov-Perel mechanism for temperatures between 77 and 300 K. However, the data suggest that electron-electron scattering should be taken into account in determining the dependence of the spin lifetime on the carrier concentration in the range 5.2x10(16)-8.8x10(17) cm(-3). For a sample with doping of 1.22x10(17) cm(-3) the spin lifetime was 24 ps at room temperature. By applying a magnetic field in the sample plane we also observed coherent precession of the spins in the time domain, with a g factor g(*)=-13, also at room temperature.

    K L Litvinenko, B N Murdin, J Allam, C R Pidgeon, M Bird, K Morris, W Branford, S K Clowes, L F Cohen, T Ashley, L Buckle (2006)Spin Relaxation in N-InSb/AlInSb Quantum Wells, In: New Journal of Physics8(4)

    We have used time resolved spectroscopy to measure the relaxation of spin polarization in InSb/AlInSb quantum wells (QWs) as a function of temperature and mobility. The results are consistent with the D'yakonov - Perel (DP) mechanism for high mobility samples over the temperature range from 50 to 300 K. For low mobility samples at high temperature the Elliott - Yafet and DP mechanisms become comparable. We show that the mobility can in certain circumstances determine which mechanism is dominant, and that above 1 m(2) V-1 s(-1) in 20 nm wide InSb QWs it is the DP mechanism. We also give a criterion for the maximum spin lifetime in terms of mobility and temperature, and show that for our 20 nm wide QWs this corresponds to 0.5 ps at 300 K and mobility 1 m(2) V-1 s(-1).

    P Murzyn, C R Pidgeon, P J Phillips, M Merrick, K L Litvinenko, J Allam, B N Murdin, T Ashley, J H Jefferson, A Miller, L F Cohen (2005)Erratum: Suppression of D'yakonov-Perel Spin Relaxation in InAs and InSb by n-Type Doping at 300 K (vol 83, pg 5220, 2003), In: Applied Physics Letters87(12)
    P. Murzyn, C. R. Pidgeon, P. J. Phillips, M. Merrick, K. L. Litvinenko, J. Allam, B. N. Murdin, T. Ashley, J. H. Jefferson, A. Miller, L. F. Cohen (2003)Suppression of D'yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K, In: Applied Physics Letters5220(2003)