Epitaxial Films of Germanium Deposited on Sapphire via Chemical Vapor Transport

Abstract

Single crystal films of germanium have been deposited on sapphire (α‐alumina) by chemical vapor transport using a disproportionation reaction involving water vapor and a technique in which the source and substrate are closely spaced. The heteroepitaxial process was found to be sensitive not only to substrate orientation and temperature, but also to impurities in the source material. Monocrystalline films were only obtained on substrates oriented in the (0001) or basal plane when heated to , and only when using source wafers heavily doped (∼1019 at./cc) with arsenic. Under identical growth conditions, polycrystalline films invariably resulted if the source materials used were either undoped, or doped with gallium, indium, or antimony in a wide range of concentrations. In addition to a high density of dislocations and low angle grain boundaries, the films also contained stacking faults of the single‐line type, believed to occur primarily as a consequence of lattice mismatch. The electrical characteristics, as well as crystalline perfection, approach that of bulk material as film thickness increases; however, p‐n junctions fabricated in these films were inferior to those formed in bulk material.