Epitaxial Ge/GaAs Heterostructures by Scanned CW Laser Annealing of a-GE Layers on GaAS

ABSTRACTEpitaxial regrowth of Ge/GaAs heterostructures by scanned laser annealing of amorphous Ge films on GaAs substrates has been studied as a function of laser power and scan rate. At least eight regimes representing different film regrowth characteristics were observed. Of these, two were of primary interest. At low powers (between~1.6 and 3.2 W for a beam diameter of~40 μm) 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 25 to 400 cm/sec, single crystal metastable (GaAs)1−x Gexalloys were obtained by liquid phase regrowth. Typical film resistivities, ρ, were as follows: as-deposited ρ=180Ωcm; polycrystalline films, ρ=3 × 10−2 Ωcm; single crystal films,ρ=9×10−4Ωcm.