We report on the photoresponse of mid-wavelength infrared radiation (MWIR) type-II superlattices (T2SLs) InAs/InAsSb high operating temperature (HOT) photoresistor grown on GaAs substrate. The device consists of a 200 periods of active layer grown on GaSb buffer layer. The photoresistor reached a 50% cut-off wavelength of 5 µm and 6 µm at 200 K and 300 K respectively. The time constant of 30 ns is observed at 200 K under 1 V bias. This is the first observation of the photoresponse in MWIR T2SLs InAs/InAsSb above 200 K.
The utmost limit performance of interband cascade detectors optimized for the longwave range of infrared radiation is investigated in this work. Currently, materials from the III–V group are characterized by short carrier lifetimes limited by Shockley-Read-Hall generation and recombination processes. The maximum carrier lifetime values reported at 77 K for the type-II superlattices InAs/GaSb and InAs/InAsSb in a longwave range correspond to ∼200 and ∼400 ns. We estimated theoretical detectivity of interband cascade detectors assuming above carrier lifetimes and a value of ∼1–50 μs reported for a well-known HgCdTe material. It has been shown that for room temperature the limit value of detctivity is of ∼3–4×1010 cmHz1/2/W for the optimized detector operating at the wavelength range ∼10 μm could be reached.
The paper reports on the barrier mid-wave infrared InAs/InAsSb (xSb = 0.4) type-II superlattice detector operating below thermoelectrical cooling. AlAsSb with Sb composition, xSb = 0.97; barrier doping, ND < 2×1016 cm−3 leading to valence band offset below 100 meV in relation to the active layer doping, ND = 5×1015 cm−3 was proved to be proper material not introducing extra barrier in valence band in the analyzed temperature range in XBn architectures. The detectivity of the simulated structure was assessed at the level of ∼ 1011 Jones at T ∼ 100 K assuming absorber thickness, d = 3 μm. The detector’s architecture for high frequency response operation, τs = 420 ps (T ∼ 77 K) was presented with a reduced active layer of d = 1 μm.
Numerical analysis of the dark current (Jd) in the type-II superlattice (T2SL) barrier (nBn) detector operated at high temperatures was presented. Theoretical calculations were compared with the experimental results for the nBn detector with the absorber and contact layers in an InAs/InAsSb superlattice separated AlAsSb barrier. Detector structure was grown using MBE technique on a GaAs substrate. The k p model was used to determine the first electron band and the first heavy and light hole bands in T2SL, as well as to calculate the absorption coefficient. The paper presents the effect of the additional hole barrier on electrical and optical parameters of the nBn structure. According to the principle of the nBn detector operation, the electrons barrier is to prevent the current flow from the contact layer to the absorber, while the holes barrier should be low enough to ensure the flow of optically generated carriers. The barrier height in the valence band (VB) was adjusted by changing the electron affinity of a ternary AlAsSb material. Results of numerical calculations similar to the experimental data were obtained, assuming the presence of a high barrier in VB which, at the same time, lowered the detector current responsivity.