GaAs, A1GaAs, and InGaAs epilayers containing As clusters: semimetal/semiconductor composites

A new kind of semiconductor composite material is demonstrated with a dispersion of semimetallic particles with properties common to high-quality single crystals. These materials are arsenides such as GaAs, AIGaAs, and InGaAs containing arsenic clusters. These composites are formed by incorporating excess As in the semiconductor, which precipitate with anneal. The incorporation of the excess As is accomplished by molecular beam epitaxy at low substrate temperatures. We demonstrate that the cluster densities can be controlled with the coarsening anneal. Furthermore, we demonstrate that heterojunctions and doping can be used to control the positioning of the As clusters.