Epitaxial Ge/GaAs heterostructures by scanned cw laser annealing of <i>a</i>-Ge layers on GaAs

Abstract

Expitaxial Ge/GaAs heterostructures have been produced by scanned cw argon laser annealing of 440-nm-thick amorphous Ge films on (100) semi-insulating GaAs substrates. Depending on the incident laser power and scan rate, two modes of film regrowth were observed. At low powers (between ∼1.6 and 4.0 W for a beam diameter of ∼40μm) and scan rates between 1 and 400 cm/sec, polycrystalline Ge with a (100) preferred orientation was formed by an ’’explosive’’ crystallization mechanism. At higher powers, and over a scan rate range of 20–400 cm/sec, single-crystal films containing some dissolved GaAs in solution were obtained by liquid phase regrowth. Typical film resistivities ρ were as follows: as-deposited, ρ = 180 Ω cm; polycrystalline films, ρ = 3×10−2 cm; single-crystal films, ρ = 9×10−4Ω cm.