Optimization of InAs/GaSb type-II superlattice interfaces for long-wave (∼8 μm) infrared detection

Optimization of various growth parameters for type-II 13 MLs InAs/7 MLs GaSb strained layer superlattices (SLSs) (λcut-off ∼8 μm at 300 K), grown by solid source molecular beam epitaxy, has been undertaken. This includes a systematic study to investigate the influence of the effect of the growth temperature and the thickness of an InSb layer formed at the GaSb-on-InAs interface on the properties of the superlattice. We present optical and structural characterization of these SLS structures, using high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and cross-sectional scanning transmission electron microscope (STEM). Optimized growth parameters were then used to grow a 2-μm-thick active region for a SLS detector designed to operate in the long-wave infrared (LWIR) region, which demonstrated full-width half-maximum (FWHM) of 16 arcsec for the first SLS satellite peak and nearly zero lattice mismatch between zero-order SLS peak and GaSb substrate.