Pushing the envelope to the maximum: Short-period InAs/GaSb type-II superlattices for mid-infrared detectors

Using a newly developed envelope function approximation model that includes interface effects, several InAs/GaSb type-II superlattices (SL) for the 4 μm (around 310 meV) detection threshold were designed. The model predicts that a given threshold can be obtained with progressively thinner SL periods and the thinner designs can have higher mobility and longer Auger lifetime over the thicker designs. The proposed SL structures were grown by molecular-beam epitaxy. The band gaps of SLs determined by low-temperature photoluminescence (PL) remained constant PL peak energy around 340-320 meV with distinctively different designs in the period range from 50.2 to 21.2 Å. Correlation between SL material quality and the full-width at half-maximum (FWHM) of the luminescence peak were made. In situ annealing after SL growth improved surface morphologies and the FWHM of the emission peak for the annealed SL samples were slightly narrower than those of non-annealed SLs.