STUDY OF 2-DIMENSIONAL HOLE GAS AT SI SIGE/SI INVERTED INTERFACE/

We have studied the transport properties of a two-dimensional hole gas (2DHG) at the inverted interface of a strained Si0.8Ge0.2 quantum wel l. By application of a bias voltage to a Schottky gate on top of this inverted heterostructure the 2DHG density n(s) can be controlled, in t he range of (1.5-5.2) x 10(11) cm(-2). At a temperature T = 0.33 K, th e Hall mobility is 4650 cm(2) V-1 s(-1) at the maximum carrier density . For lower sheet densities (n(s) < 2 x 10(11) cm(-2)) the system unde rgoes a transition from a weak to strongly localised phase of signific antly reduced mobility. From low temperature Shubnikov-de Raas oscilla tion measurements we have extracted the hole effective masses m = (0. 25 --> 0.28)m(0) and the ratio of transport to quantum lifetimes alpha = (0.92 --> 0.85) for the corresponding carrier density change of n(s ) = (5.2 --> 2.5) x 10(11) cm(-2). These results can be explained in t erms of the abnormal movement of the hole wave function towards the in terface with decreasing n(s), short range interface charge and interfa ce roughness scattering.