Influence of interace and buffer layer on the structure of InAs/GaSb superlattices

Abstract

Using image processing algorithms based on nonlinear imaging theory, we have analyzed high-resolution transmission electron microscopy images of InAs/GaSb superlattices (SLs) grown by molecular beam epitaxy. Our analysis indicates that InSb-like interfaces have a roughness of 1 monolayer (ML), for a SL grown on a GaSb buffer layer. For GaAs-like interfaces, however, the interface roughness is found to be 2 MLs when the SL is grown on a GaSb buffer. For SLs grown on an InAs buffer, the roughness of GaAs-like interfaces (3 MLs) is also greater than that of InSb-like interfaces (2MLs). These results suggest two general observations. The first is that GaAs-like interfaces are rougher than InSb-like interfaces. This difference may be due to the high surface energy of GaAs as compared to InSb. The second observation is that interface roughness is greater for an InAs/GaSb SL grown on an InAs buffer layer than for the same SL grown on a GaSb buffer layer. This difference in interface roughness may be due to InAs SL layers being in tension when grown on a GaSb buffer layer, whereas GaSb SL layers are under compression when grown on an InAs buffer layer.