Interface structures of III-V semiconductor heterostructures

We report first-principles calculations of the electronic and geometric structure of the (110) cross-sectional surfaces on InAs/GaSb superlattices and compare the results to scanning tunneling microscopy images of filled electronic states. We also study the atomic scale structure of (001) interface surfaces and the adsorption of deposited atoms on these surfaces to simulate the process occurring during the heterostructure growth. In both the predicted and measured images the InAs (110) surfaces appear lower than GaSb, a height difference we show is caused primarily by differences in the electronic structure of the two materials. In contrast, local variations in the apparent height of (110) surface atoms at InSb- or GaAs-like interfaces arise primarily from geometric distortions associated with local differences in bond length. We further observed that both Ga- and Sb-terminating (001) surfaces showed dimerization of surface atoms. Ga-terminating (001) surfaces exhibited substantial buckling of surface atoms while Sb-terminating (001) surfaces did not show appreciable buckling. The adsorption of arsenic atoms occurred preferably at the bridge sites between the dimerized Sb atoms on Sb-terminating (001) surfaces. Indium atoms, on the other hand, were observed to have somewhat equal probabilities to be adsorbed at a few different sites on Ga-terminating (001) surfaces. Our calculated energies for atomic intermixing indicate that anion exchanges are exothermic for As atoms on Ga-terminating (001) interfaces but endothermic for In atoms on Sb-terminating (001) interfaces. This difference may explain why GaAs interfaces are typically more disordered than InSb interfaces in these heterostructures. (C) 2003 Wiley Periodicals, Inc.