Design of InAs/GaSb type-II superlattice (T2SL) infrared barrier detectors is theoretically investigated.Each part of the barrier structures is studied in order to achieve optimal device operation at 150K and 77K, in the midwave and longwave infrared domain, respectively. Whatever the spectral domain, nBp structure with a p-type absorbing zone and an n-type contact layer is found to be the most favourable detector architecture allowing a reduction of the dark-current associated with generation-recombination processes. The nBp structures are then compared to pin photodiodes. The MWIR nBp detector with 5 µm cut-off wavelength can operate up to 120K, resulting in an improvement of 20K on the operating temperature compared to the pin device. The dark-current density of the LWIR nBp device at 77K is expected to be as low as 3.5 x 10 -4 A/cm 2 at 50 mV reverse bias, more than one decade lower than the usual T2SL photodiode. This result, for a device having cut-off wavelength at 12 µm, is at the state of the art compared to the well-known MCT 'rule 07'. Highlights :1-InAs/GaSb type-II superlattice barier detectors have been designed for the MWIR and for the LWIR 2-MWIR nBp T2SL detector can operate up to 120K 3-LWIR nBp T2SL detector can compete with well established MCT technology.

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GaSb-rich superlattice (SL) p-i-n photodiodes grown by molecular beam epitaxy were studied theoretically and experimentally in order to understand the poor dark current characteristics typically obtained. This behavior, independent of the SL-grown material quality, is usually attributed to the presence of defects due to Ga-related bonds, limiting the SL carrier lifetime. By analyzing the photoresponse spectra of reverse-biased photodiodes at 80 K, we have highlighted the presence of an electric field, breaking the minibands into localized Wannier-Stark states. Besides the influence of defects in such GaSb-rich SL structures, this electric field induces a strong tunneling current at low bias which can be the main limiting mechanism explaining the high dark current density of the GaSb-rich SL diode.

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