High-Quality, Thin-Film Germanium Single Crystals

Germanium (Ge) has crystallographic characteristics similar to GaAs and compatible with heteroepitaxial growth of GaAs. Further, since efficient heteroface cells already grown on thick Ge single crystals, Ge is excellent substrate candidate for thin-film cells. Required is single-crystal Ge thin film. Method developed for epitaxially growing highquality 10-um Ge thin films on ,100. NaCl substrates by plasma-enhanced chemical-vapor deposition (PECVD) and then separating Ge films by either melt-away or differential-thermal shear stress techniques. Free-standing films used for growth of AlxGa1-xAs/GaAs heteroface cells by similar techniques.