MBE growth of high quality AllnSb/GaSb compound buffer layers on GaAs substrates

摘要

The epitaxy properties of GaAs-based GaSb thin films were investigated under different growth conditions to identify suitable smooth areas on GaSb epilayer surface for growing high-quality AllnSb metamorphic buffers. The results showed notable reduction in threading dislocation densities (TDDs) and hillocks densities (HDs) of GaSb buffer layer when the temperature of substrates rising to Tc (surface reconstruction conversion temperature) + 110 ℃ and growth rate decreasing to 0.25 mono layer per second (ML/s). These conditions led to gradual changes in GaSb epilayer surface morphologies from tiny hillocks to near-parallel steps. The AllnSb/GaSb compound buffers were studied by employing five different structures of AllnSb metamorphic buffer layers grown on optimized GaSb layers, and then analyzed by various analytical methods. The influence of various structural buffer layers on defects were evaluated in order to suppress the formation of defects. It was shown that the buffer layer with low-temperature interface layer and superlattice structure presents obvious inhibitory effects on defects. Among these, specimens with superlattice interface exhibits the lowest TDDs of 3.1 × 10~7 cm~(-2) and moderate HDs of 2.4 × 10~7 cm~(-2).