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This paper reports on the unipolar medium wavelength infrared (MWIR) InAs/GaSb/B-Al0.2Ga0.8Sb type-II superlattice (T2SL) nBn detector's photoelectrical performance. In our model, the heterojunction barrier-active region (absorber) was assumed to be decisive as the contributing dark current mechanism limiting nBn's detector performance. The voltage drop analysis on the nBn structure was introduced to estimate the bias drop on the heterojunction barrier-active region. It was assumed that the contact n+-barrier heterojunction's layer has an insignificant influence on the electrical properties of the detector. In addition, a bulk-based model with an effective band gap of T2SL material has been assumed in the device modeling. Both current-voltage (I-V) and differential resistance-area product RA(V,T), characteristics of nBn's detector were found to be dominated by diffusion and generation-recombination currents in the zero-bias and the low-bias regions. At medium values of reverse voltages, the dark current was mostly affected by trap-assisted tunneling, whereas the band-to-band tunneling revealed its contribution at high values of reverse bias (V > 0.7 V). The RA(V,T) characteristics' fitting procedure allowed estimation of both diffusion and generation-recombination lifetimes as well as the trap energy level temperature dependence within T2SL energy gap. It was predicted that at T = 77 K, the RA product and detectivity reached values of 1000 &Ohgr;cm2 and 4 × 1011 cm Hz1/2 W-1, respectively. The corresponding values at room temperature were 0.01 &Ohgr;cm2 and D* = 5 × 108 cmHz1/2 W-1, respectively. Finally, InAs/GaSb/B-Al0.2Ga0.8Sb T2SLs nBn's state of the art was compared to the performance of InAs/GaSb T2SLs PIN photodiodes and the HgCdTe bulk photodiodes operated at near-room temperature. It was shown that the RA product of the MWIR T2SLs nBn detector has reached a comparable level with the state of the art of the HgCdTe bulk photodiodes. [ABSTRACT FROM AUTHOR]

The temperature-dependent behaviour of the bandgap of mid- and long-wavelength as well as dual-colour (mid-/long-wavelength) infrared detectors based on InAs/GaSb strained layer superlattices (SLSs) with p-i-n and nBn designs has been investigated with temperature-dependent absorption, photoluminescence and spectral response techniques. Values of Varshni parameters, zero temperature bandgap E0 and empirical coefficient α, were extracted and tabulated. The MWIR and LWIR superlattice detectors showed a temperature change of 0.325 meV K−1 and 0.282 meV K−1, respectively. These values are a factor of two lower than that of HgCdTe and InSb, making them attractive for higher operating temperatures. [ABSTRACT FROM AUTHOR]