Professor Jeremy Allam
Professor of Ultrafast Optoelectronics
Qualifications: MA (Oxon), PhD (Surrey), MInstP, CPhys, MIEEE, MIEE
Email: j.allam@surrey.ac.uk
Phone: Work: 01483 68 6799
Room no: 13 ATI 01
Further information
Biography
Jeremy Allam obtained his first degree in Physics from the University of Oxford, and his PhD from Surrey. After working for 2 years at AT&T Bell Laboratories and for 3 years as a postdoc sponsored by British Telecom, in 1990 he joined the newly-formed Hitachi Cambridge Laboratory where he formed a group working in Femtosecond Optoelectronics. In April 2000 he was appointed to a Chair in Ultrafast Optoelectronics.
Research Interests
Jeremy's research interests include ultrafast carrier dynamics in semiconductors for optoelectronic devices, high-speed photonic measurement technologies, and high-field carrier transport. He has recently commissioned a a new ultrafast laser facility comprising laser oscillators and amplifiers, parametric oscillators and amplifiers, and frequency mixers, providing a capability for <100 fs optical pulses from UV to the mid-IR wavelengths.
Research Collaborations
A full list of publications, conference presentations, and patents can be found here.
Publications
Highlights
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(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 7726doi: 10.1117/12.853912Full text is available at: http://epubs.surrey.ac.uk/733177/
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.
- . (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.
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(2008) 'Temperature dependence of the electron Lande g factor in InSb and GaAs'. AMER PHYSICAL SOC PHYSICAL REVIEW B, 77 (3) Article number ARTN 033204 Full text is available at: http://epubs.surrey.ac.uk/217915/
- . (2007) 'Spin dynamics in narrow-gap semiconductor epitaxial layers'. SPRINGER JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, Maui, HI: 4th International School and Conference on Spintronics and Quantum Information Technology (Spintech IV) 20 (6), pp. 461-465.
Journal articles
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(2012) 'Improved optoelectronic properties of rapid thermally annealed dilute nitride GaInNAs photodetectors'. Journal of Electronic Materials, 41 (12), pp. 3393-3401.Full text is available at: http://epubs.surrey.ac.uk/745030/
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.
- . (2011) 'GaInNAsSb/GaAs Photodiodes for Long-Wavelength Applications'. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE ELECTRON DEVICE LETTERS, 32 (7), pp. 919-921.
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(2008) 'Temperature dependence of the electron Lande g factor in InSb and GaAs'. AMER PHYSICAL SOC PHYSICAL REVIEW B, 77 (3) Article number ARTN 033204 Full text is available at: http://epubs.surrey.ac.uk/217915/
- . (2007) 'GaInNAs lattice-matched to GaAs for photodiodes'. Conference Proceedings - International Conference on Indium Phosphide and Related Materials, , pp. 347-349.
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(2006) 'Two- and one-dimensional light propagations and gain in layer-by-layer-deposited colloidal nanocrystal waveguides'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 89 (11) Article number ARTN 111120 doi: 10.1063/1.2354433
- . (2006) 'Spin lifetime in InAs epitaxial layers grown on GaAs'. AMERICAN PHYSICAL SOC PHYSICAL REVIEW B, 74 (7) Article number ARTN 075331
- . (2006) 'Spin relaxation in n-InSb/AlInSb quantum wells'. IOP PUBLISHING LTD NEW JOURNAL OF PHYSICS, 8 Article number PII S1367-2630(06)15617-7
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(2006) 'Resonant tunnelling and fast switching in amorphous-carbon quantum-well structures'. NATURE PUBLISHING GROUP NATURE MATERIALS, 5 (1), pp. 19-22.doi: 10.1038/nmat1551
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(2006) 'Coherent generation and control of long-lived ultra-short transients in a semiconductor laser - art. no. 61840M'. SPIE-INT SOC OPTICAL ENGINEERING Semiconductor Lasers and Laser Dynamics II, Strasbourg, FRANCE: 6184 Article number 61840M , pp. M1840-M1840.doi: 10.1117/12.663169
Conference papers
- . (2010) 'Reaction, diffusion and dissociation of excitons on carbon nanotubes'. The Optical Society OSA Technical Digest (CD), San Jose, California, USA: CLEO/QELS: 2010 Laser Science to Photonic Application
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(2010) 'InGaAsN as absorber in APDs for 1.3 micron wavelength applications'. Kagawa, Japan: IPRM 2010, pp. 187-190.Full text is available at: http://epubs.surrey.ac.uk/733524/
Abstract
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.
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(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 7726doi: 10.1117/12.853912Full text is available at: http://epubs.surrey.ac.uk/733177/
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.
- . (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.
- .
(2008) 'Dark current mechanisms in bulk GaInNAs photodiodes'. IEEE Proccedings of 20th International Conference on Indium Phosphide and Related Materials, Versailles, France: IPRM 2008Full text is available at: http://epubs.surrey.ac.uk/733530/
Abstract
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.
- . (2008) 'Density and well-width dependence of the spin relaxation in n-InSb/AlInSb quantum wells'. SPRINGER NARROW GAP SEMICONDUCTORS 2007, Guildford, ENGLAND: 13th International Conference on Narrow Gap Semiconductors 119, pp. 19-21.
- . (2007) 'Spin dynamics in narrow-gap semiconductor epitaxial layers'. SPRINGER JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, Maui, HI: 4th International School and Conference on Spintronics and Quantum Information Technology (Spintech IV) 20 (6), pp. 461-465.
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(2007) 'Spin lifetime in high quality InSb epitaxial layers grown on GaAs'. AMER INST PHYSICS JOURNAL OF APPLIED PHYSICS, 101 (8)doi: 10.1063/1.2719017
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(2005) 'Coherent interactions and long term evolution of ultrafast transients in a semiconductor laser'. IEEE 2005 IEEE LEOS Annual Meeting Conference Proceedings (LEOS), Sydney, AUSTRALIA: 18th Annual Meeting of the IEEE-Lasers-and-Electro-Optical-Society, pp. 823-824.Full text is available at: http://epubs.surrey.ac.uk/1558/