Epitaxial GaAs Films Deposited by Vacuum Evaporation

Epitaxial films of GaAs have been vacuum-deposited onto GaAs and Ge single-crystal substrates by a modified three-temperature-zone technique. The film properties have been investigated by reflection electron diffraction (RED) and also optically. At a deposition temperature of 375°C the films possess [100] fiber textures; below 375°C, the film properties follow those deposited on amorphous substrates. At 400°C the films become epitaxial with twinning on all (111) planes. Between 425° and 450°C, the films are highly ordered, twin free, on the b faces of GaAs and on Ge; in the same temperature range, thick films (> 10 000 Å) and films deposited on a faces of GaAs exhibit extra reflections in RED and departures from the expected optical behavior. Films deposited above 450°C, under conditions for which excess Ga may exist, grow in an hcp modification; the reflectivity of these films agrees with bulk zinc blende GaAs.