Surface and Interface Studies of Compound Semiconductors.

The geometric and electronic properties of compound semiconductor surfaces and interfaces were studied using experimental techniques such as electron and x-ray diffraction, Auger spectroscopy, synchrotron photoemission, and scanning tunneling microscopy. Some of the surface and interfacial properties this thesis is concerned with include clean and adsorbate-induced reconstructions, valence-band discontinuities and Schottky-barrier formations, doping and metallization, work function changes and growth considerations. Experiments were performed on the Sb-stabilized GaSb(100)-(1 x 3) surface grown by molecular beam epitaxy. Bulk valence bands were mapped out in the Gamma -Delta-X direction. The deconvoluted Sb-4d and Ga-3d core-level line shapes were used to construct a structural model for the surface. STM resolved the individual atomic dimers verifying the proposed model and showed partial disorder inherent on this surface. The interaction of the clean GaSb(100) surface with ZnTe, a strain-free (i.e. highly lattice-matched) system, was explored using synchrotron photoemission. The deconvoluted core-level line shapes were used to construct structural models for the interface between these compound semiconductors in both the high and low-temperature growth phases. In addition, the movement of the valence band and Fermi level was used to examine the heterojunction band offset for the low-temperature phase and the dopant incorporation for the high-temperature phase. The interface between an alkali metal, cesium, and the clean GaSb(100) surface was investigated up to its saturation limit. The work function change was measured and the Fermi level movement determined the degree of surface metallicity. Core level line shapes were used to determine surface structure as well as the degree of charge transfer. Finally, the interface formation and subsequent growth of InSb on vicinal (4^circ off) and on-axis Si(100), a strained system (i.e. highly lattice-mismatched), was studied. During the initial stages of molecular beam epitaxy at 410^circ C we examined the In, Sb, and Si core levels as a function of In and Sb coverage and deposition order. Based on these results a model for interface formation was developed. Thicker coverage results of co-evaporated InSb are discussed in light of the interfacial analyses.