In this work we report simulation and experimental results for an MWIR HgCdTe photodetector designed by computer simulation and fabricated in a joint laboratory run by VIGO Sytems S.A. and Military University of Technology. The device is based on a modified N+pP+ heterostructure grown on 2”., epiready, semi-insulating (100) GaAs substrates in a horizontal MOCVD AIX 200 reactor.

The devices were examined by measurements of spectral and time responses as a function of a bias voltage and operating temperatures. The time response was measured with an Optical Parametric Oscillator (OPO) as the source of ~25 ps pulses of infrared radiation, tuneable in a 1.55–16 μm spectral range. Two-stage Peltier cooled devices (230 K) with a 4.1 μm cut-off wavelength were characterized by 1.6 × 1012 cm Hz1/2/W peak detectivity and < 1 ns time constant for V > 500 mV.

The performance of long-wave infrared (LWIR) x = 0.22 HgCdTe avalanche photodiodes (APDs) was presented. The dark current-voltage characteristics at temperatures 200 K, 230 K, and 300 K were measured and numerically simulated. Theoretical modeling was performed by the numerical Apsys platform (Crosslight). The effects of the tunneling currents and impact ionization in HgCdTe APDs were calculated. Dark currents exhibit peculiar features which were observed experimentally. The proper agreement between the theoretical and experimental characteristics allowed to determine the material parameters of the absorber was reached. The effect of the multiplication layer profile on the detector characteristics was observed but was found to be insignificant.

A theoretical analysis of the mid-wavelength infrared range detectors based on the HgCdTe materials for high operating temperatures is presented. Numerical calculations were compared with the experimental data for HgCdTe heterostructures grown by the MOCVD on the GaAs substrates. Theoretical modelling was performed by the commercial platform SimuAPSYS (Crosslight). SimuAPSYS fully supports numerical simulations and helps understand the mechanisms occurring in the detector structures. Theoretical estimates were compared with the dark current density experimental data at the selected characteristic temperatures: 230 K and 300 K. The proper agreement between theoretical and experimental data was reached by changing Auger-1 and Auger-7 recombination rates and Shockley-Read-Hall carrier lifetime. The level of the match was confirmed by a theoretical evaluation of the current responsivity and zero-bias dynamic resistance area product (R0A) of the tested detectors.

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.

Current advances in type-II superlattice (T2SL) research at Fraunhofer IAF are elaborated on in this paper. First, the use of metastructures for quantum efficiency (QE) enhancement in the longwave infrared (LWIR) is presented. Finite element modelling results are reported on that suggest a potential for doubling of the QE at certain wavelengths with the investigated device structure. Next, characterisation results of midwave infrared (MIWR) InAs/InAsSb T2SL nBn detectors are shown. The low, diffusion-limited dark current above 120 K and a QE of 60% are comparable to the state-of-the-art. Finally, groundwork for InAs/GaSb T2SL MWIR/LWIR dual-band detector arrays based on a back-to-back heterojunction diode device concept is presented. The dry etching technology allows for steep etch trenches and full pixel reticulation with a fill factor of about 70% at 12 µm pitch. The detector characterisation at 77 K and ±250 mV bias demonstrates the bias-switchable operation mode with dark current densities of 6.1·10−9 A/cm² in the MWIR and 5.3·10−4 A/cm² in the LWIR.

The paper reports on the barrier mid-wave infrared InAs/InAsSb (x_Sb = 0.4) type-II superlattice detector operating below thermoelectrical cooling. AlAsSb with Sb composition, x_Sb = 0.97; barrier doping, N_D < 2×10¹⁶ cm⁻³ leading to valence band offset below 100 meV in relation to the active layer doping, N_D = 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, τ_s = 420 ps (T ∼ 77 K) was presented with a reduced active layer of d = 1 μm.