Atomic and Electronic Structure of Compound Semiconductor Interfaces

Abstract

The cleavage faces of zincblende and wurtzite structure compound semiconductors constitute the best understood of all semiconductor interfaces. Structure determinations by low-energy electron diffraction and ion-scattering of the zincblende (110) cleavage surfaces reveal not only greatly distorted surface geometries relative to the bulk, but also the unanticipated result that III–V and II–VI compounds exhibit comparable surface structures in contrast to their quite different molecular geometries. This observation motivated an extensive theoretical effort to predict these structures, with the result that an electronically driven atomic relaxation phenomenon provides a common quantitative description of all the experimental data. Extension of this theory to wurtzite ($10\bar 10$) and ($10\bar 20$) cleavage faces reveals an analogous mechanism for relaxations at these surfaces, as well as the existence for each surface of a unique atomic geometry, determined by the atomic connectivity of the truncated bulk surface, which depends on the specific material only via a linear scaling with the bulk lattice constant. Further extensions of the theory and structure analyses to interface geometries, specifically Sb on GaAs(110) and InP(110), reveal the existence of a new type of epitaxically mediated pi bond of (1×1) overlayers of Sb on GaAs and InP. Therefore the determination and prediction of surface atomic geometries have disclosed unanticipated types of chemical bonding which exhibit neither bulk nor molecular analogs.