Physics Chat
Theoretical modelling of a type-II InAs/GaSb superlattice for long-wavelength infrared detectors
Speaker: Paradeisa O'Dowd-Phanis (M Kesaria)
Date: Friday 4 March 2022
Time: 15:00
Venue: Zoom
There is an extensive amount of information that is invisible to the human eye in the form of infrared (IR) radiation. This can be accessed through the use of IR photon detectors. The state-of-the-art for IR photon detectors consists of an active region made of Mercury Cadmium Telluride (MCT). However, there are problems with this material system, such as uniformity issues, as small variations in composition can cause significant changes in cut off wavelength, high cost, due to the substrate on which it is grown, and high levels of tunnelling current, stemming from Auger recombination. Due to the various drawbacks of this material, there have been several alternatives proposed. Type-II superlattices (T2SL) made of InAs/GaSb were first proposed by Sai-Hakasz et. al. [1] in 1970, since then they have garnered increasing attention over the past few decades due to easier and cheaper manufacturability as well as Auger recombination suppression. For long-wavelength infrared (LWIR) detectors the InAs/GaSb T2SL has been the most promising candidate, however, the predicted theoretical performance levels have yet to be achieved due to deleterious Ga-related defects which reduce the minority carrier lifetime. Theoretical modelling of T2SLs and device schemes can result in improved detector performance. Designing the optimum repeat and thickness in T2SL for the desired cutoff wavelengths can increase wavefunction overlap, by tuning the effective carrier mass and the tunnelling probability. The 8-band k.p method was applied in order to calculate the electronic band structure (E(k) dispersion curve) of the T2SLs and study their properties [2, 3]. Figure 1 shows the modelled T2SL electron effective mass against the energy bandgap. References: [1] Sai-Halasz G.A. et al. (1977) Appl. Phys. Lett. 30, 651 [2] Delmas M. et al. (2019) Proc. SPIE 10926, Quantum Sensing and Nano Electronics and Photonics XVI, 109260G [3] Manyk T. et al. (2018) Results in Physics 11, 1119-1123 .
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