Schottky gating high mobility Si/Si1−xGex 2D electron systems

Abstract A high mobility (3.6×10 5 cm 2 /V s) n-type Si/Si 1− x Ge x heterostructure has been Schottky gated using Au metal to cover the whole of the device. Over the front-gate voltage ( V g ) range for which there was negligible gate leakage (−0.1 V V g 11 to 4.4×10 11 cm −2 . Measurements of the quantum lifetime suggested that the quality of the device varied in a manner not indicated by the transport mobility. This may arise from inhomogeneities caused by energy-level broadening. The results can be explained by a surface-roughened Au gate whose influence is negated at zero front-gate voltage due to a frozen-in screening charge in the doping layer.