Ultra-high hole mobility exceeding one million in a strained germanium quantum well

In this paper, we report a Hall mobility of one million in a germanium two-dimensional hole gas. The extremely high hole mobility of 1.1 x 10(6) cm(2) V-1 s(-1) at a carrier sheet density of 3 x 10(11) cm(-2) was observed at 12K. This mobility is nearly an order of magnitude higher than any previously reported. From the structural analysis of the material and mobility modeling based on the relaxation time approximation, we attribute this result to the combination of a high purity Ge channel and a very low background impurity level that is achieved from the reduced-pressure chemical vapor deposition growth method. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4763476]