Atomically smooth interfaces of type-II InAs/GaSb superlattice on metamorphic GaSb buffer grown in 2D mode on GaAs substrate using MBE

摘要

In the paper, the comparative analysis of type-II InAs/GaSb SLs deposited on three types of GaSb buffers: homoepitaxial, metamorphic and one grown using the interfacial misfit (IMF) array technique has been presented. The buffer layers as well as superlattices were grown under nominally identical technological conditions. HRXRD investigations proved better crystal quality of the metamorphic material than the IMF-GaSb. FWHMRC were equal to 156 arcsec and 196 arcsec, respectively. The surface roughness of about 1 ML and 4 MLs was obtained using the atomic force microscope for 4.0 mu m-metamorphic GaSb and 1.5 mu m-IMF-GaSb layers, respectively. The etch pits density for both buffers was similar, 1-2 x 10(7) cm(-2). Superlattice with 500 periods deposited on the homoepitaxial buffer was used as a reference of the best crystal quality. HRTEM images revealed straight InAs/GaSb interfaces with 1 ML thicknesses in this sample. The interfaces in SL deposited on IMF-GaSb buffer were undulated and smeared over 3 MLs. The use of the metamorphic buffer resulted in 1-2 ML straight InAs/GaSb interfaces. The main reason for this is the roughness of IMF-GaSb buffer with mounds on the surface. Based on the obtained results we have demonstrated the advantage of metamorphic approach over IMF growth mode in GaSb/GaAs material system. A two times thicker buffer could be the price worth paying for high quality structures, even when working in the production mode.