High room-temperature hole mobility in Ge0.7Si0.3/Ge/Ge0.7Si0.3 modulation-doped heterostructures

Modulation-doped two-dimensional hole gas structures consisting of a strain ed germanium channel on relaxed Ge0.7Si0.3 buffer layers were grown by mole cular-beam epitaxy. Sample processing was optimized to substantially reduce the contribution from the parasitic conducting layers. Very high hall mobi lities of 1700 cm(2)/V s for holes were observed at 295 K which are the hig hest reported to date for any kind of p-type silicon-based heterostructures . Hall measurements were carried out from 13 to 300 K to determine the temp erature dependence of the mobility and carrier concentration. The carrier c oncentration at room temperature was 7.9 x 10(11) cm(-2) and decreased by o nly 26% at 13 K, indicating very little parallel conduction. The high-tempe rature mobility obeys a T-alpha behavior with alpha similar to 2, which can be attributed to intraband optical phonon scattering. (C) 2001 American In stitute of Physics.