Strucrural properties of GaSb layers grown on InAs, AlSb, and GaSb buffer layers on GaAs (001) substrates

The strain-relief and the structural properties of GaSb films with thin InAs, AlSb, and GaSb buffer layers grown on GaAs (001) substrates at low temperature (LT) by molecular beam epitaxy were investigated using atomic force microscopy, transmission election microscopy, and X-ray diffraction. The strain arising from depositing the thin buffer layer onto the GaAs substrate was relieved by a periodic array of 90 degrees misfit dislocations with a Burgers vector of 1/2a < 110 > for the AlSb/GaAs and the GaSb/GaAs systems, but by both 60 degrees and 90 degrees misfit dislocations for the InAs/GaAs system. The 90 degrees misfit dislocation arrays at the AlSb/GaAs and GaSb/GaAs interface had average spacing of 4.80 nm and 5.59 nm, respectively. The mean roughnesses and the full widths at half maximum of the rocking curves of the GaSb films on the thin AlSb and GaSb buffer layers were found, respectively, to be less than I nm and about three times lower than the corresponding values for the system with an InAs buffer layer. These results clearly demonstrate that the presence of a thin, low-temperature AlSb or GaSb buffer layer is very useful for improving the quality of GaSb crystals grown on GaAs substrates.