Comparison of the electro-optical performances of symmetrical and asymmetrical MWIR InAs/GaSb superlattice pin photodiodes

We report the full electrooptical characterization of two MWIR InAs/GaSb superlattice (SL) pin photodiodes. The first one features a symmetrical period with 8 InAs monolayers (MLs) and 8 GaSb MLs, while the second one relies on an asymmetrical period with 7.5 InAs MLs and 3.5 GaSb MLs. This asymmetrical design was recently proposed by IES to both decrease the dark current (since it decreases the intrinsic carrier concentration) and increase the quantum efficiency (since it increases the wavefunctions overlap). We present dark current, noise, spectral response and quantum efficiency measurements. Our results confirm that the asymmetrical design allows to greatly improve the performance of MWIR SL pin photodiodes, with an improvement of more than one decade in terms of dark current and an improvement of a factor 1.5 in terms of quantum efficiency. The noise measurements under dark conditions show that the symmetrical (asymmetrical) sample remains Schottky noise-limited up to a bias voltage of -600mV (resp -800mV) and that 1/f noise remains very low.