High electron mobilities in surfactant-grown germanium on silicon substrates

We present the first investigation of the electrical properties of relaxed Ge layers grown on Si(111) substrates by surfactant-mediated epitaxy with Sb. Electron Hall mobilities and carrier concentrations of 1 mu m thick epitaxial Ge layers grown on p-type Si-substrates at temperatures between 640 degrees C and 720 degrees C were determined at 300 It and 77 K. The highest electron mobilities, 3100 cm(2)/Vs and 12300 cm(2)/Vs, at 300 K and 77 K, were observed in the 720 degrees C sample. At 300 K an electron concentration of only 1.1x10(16) cm(-3) was measured suggesting a substantially lower incorporation of the surfactant Sb compared to earlier publications. The low Sb doping was independently supported by secondary ion mass spectroscopy (SIMS).