Pulsed laser crystallization and structuring of a-Ge on GaAs

Abstract

We have investigated the crystallization and structuring of amorphous Ge (a-Ge) films deposited on crystalline GaAs (1 0 0) substrates by nanosecond laser pulses. Epitaxial Ge films on GaAs are obtained for laser fluencies that completely melt the Ge film, but not the substrate. Higher fluencies lead to a partial melting of the substrate and to the formation of a (GaAs) 1− x Ge 2 x epitaxial alloy at the interface with the substrate. We demonstrate the fabrication of line gratings of crystalline Ge on GaAs produced by laser interference structuring. The gratings display an unusual surface undulation with faceted surfaces, which is ascribed to a lateral solidification process.