LONG-WAVELENGTH TYPE-II INAS/GASB SUPERLATTICE INFRARED PHOTODETECTORS

Lead Research Organisation: Cardiff University
Department Name: School of Physics and Astronomy

Abstract

Crucial information from our environment is in the infrared spectral domain, which we cannot see with our eyes; infrared photodetectors are therefore essential to go beyond human capacity. The need for high performance detectors, i.e. quantum (photonic) infrared detectors with high detectivity (low dark current and high quantum efficiency), for specific military (soldier vision enhancement, missile tracking/seeker) and space (earth observation) applications, are increasingly relevant. This PhD research project will focus on Type-II InAs/GaSb SuperLattice (T2SL) material as the device absorption region since it is considered a promising candidate for the next generation of high performance infrared imaging systems (high operating temperature, multispectrality, large focal plane array).
Thanks to its unique properties, this material has proven to have the potential to outperform, in the long-wavelength infrared (LWIR) spectral domain, state-of-the-art infrared technologies such as Mercury Cadmium Telluride and GaAs/GaAlAs Quantum Well Infrared Photodetector. However, up to now its theoretical performance has not yet been reached; this is directly related to the low minority carrier lifetime due to defects in the T2SL material. Our approach to achieve high performance detectors (dark current level < 10-4 A/cm2 for a cut-off wavelength of 12 um at 77K) is therefore to investigate the defect levels and types in the material grown by Molecular Beam Epitaxy (MBE) and their influence on the device performance - which is not well understood yet, and to use the flexibility of the T2SL material and the 6.1 Angstrom materials family (including InAs, GaSb and AlSb semiconductor material) to realize novel structures such as barrier devices that overcome the short-comings of standard pn homojunctions and thus allow us to improve performance. Moreover, we will explore different substrates (GaSb, GaAs) on which the T2SL is grown and identify the optimum combination of substrate (material, type, orientation) and device design.
The research project is composed of four interdisciplinary tasks:
(1) T2SL growth by MBE and material characterization (high resolution X-ray diffraction, transmission electron microscopy, atomic force microscopy, photoluminescence, etc.);
(2) Detector fabrication in cleanroom which includes standard photolithography process, etching, metallization;
(3) Electro-optical characterizations such as current-voltage, capacitance-voltage, spectral response measurements;
(4) Design and simulation of T2SL infrared detectors;
The EPSRC Studentship will be conducted in collaboration between Prof. Huffaker's lab at Cardiff University and IQE's Infrared Business. The student will have excellent technical and mentoring support from Huffaker team members with expertise in nano-devices, III-V (T2SL) infrared photodetectors, and MBE epitaxy. Dr. Peter Hargrave as second supervisor will provide additional support in device design and requirements for LWIR photodetectors. Third supervisor Dr. Mark Furlong from IQE's Infrared Business will complete the team by enabling advice and guidance on the material science aspects of epitaxial growth and substrate technology that will support the fabrication of high performance detectors. Furthermore, the student will have access to state-of-the-art cleanroom facilities and equipment within the Institute for Compound Semiconductors to conduct their research. This experienced supervisory team and world class access to facilities ensures a very high chance of successful completion of the project within 4 years.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512503/1 01/10/2017 30/09/2021
2109808 Studentship EP/R512503/1 01/10/2018 31/03/2022 Dominic Chee Kwan