Growth of short-period InAs∕GaSb superlattices

Abstract

The purpose of this work is to explore materials for midinfrared detectors that can operate at room temperature. Shorter-period InAs∕GaSb superlattices (SLs) have larger intervalance band separations, which are beneficial for reducing Auger recombination and tunneling current, thus making room temperature operation possible. To test these possibilities, several short-period SLs ranging from 50to11Å were grown and their morphological properties were carefully monitored by transmission electron microscopy. The effect of structural degradation caused by the period reduction on the optical properties was studied using low-temperature photoluminescence (PL). The samples with larger periods (50–32Å) showed excellent structural qualities and produced narrow full width at half maximum (FWHM) of the PL peak (5meV). As the period approached 24Å, slight layer thickness undulations within the SLs were observed and these undulations intensified as the period further reduced to 17Å. These structural degradations strongly influence optical properties causing significant broadening in the FWHM and higher residual carrier concentration in the shorter-period SLs. With slower growth rates, samples with periods as thin as 19Å were grown without significant layer undulations.