DESIGNER INTERFACES IN II-VI/III-V-POLAR HETEROEPITAXY

The development of composite materials incorporating both II-VI and III-V compound semiconductors, such as ZnSe and GaAs, leads to the possibility of a variety of new devices of potential importance to the communications industry. In many cases, such as those involving resonant tunneling junctions and quantum well structures, the quality of the interface between the different compound semiconductors determines the ultimate quality of the device itself. Therefore, we have investigated the factors determining this interface quality for the GaAs/ZnSe system as prepared by molecular beam epitaxy. In this system, the stoichiometry of the substrate is of paramount importance. An excess of one constituent leads to high local electrical fields and poor interface morphology. Optimum growth of ZnSe on GaAs is achieved with GaAs substrate surfaces having a stoichiometry intermediate between the As- and Ga-rich extremes. We will describe a model that defines the conditions for good interface formation and summarize experimental evidence which supports the validity of this model.