Band Structure Investigation on p-Type Silicon Inversion Layers by Piezoresistance and Mobility Measurements

Abstract

Piezoresistance and mobility measurements have been performed between 310 and 77 °K with p-type inversion layers on (100), (110), and (111) silicon. An explanation of the dependences on the gate voltage (perpendicular electric field) can be given by the interaction of the quantized heavy (HHB) and light hole bands (LHB) at the surface. The interface stress caused by the insulating layer removes the valence band degeneracy, which results in ellipsoidal energy surfaces. By use of this model the energy positions of the subbands have been calculated. The state of degeneracy is found at higher gate fields. These theoretical results make it possible to interpret as well anomalies in piezoresistance as the initial rise and orientation anisotropies of the mobility. The ratio of heavy and light holes taking part in the transport have been deduced as a function of the gate voltage. The influence of the band-band scattering between LHB and HHB will be discussed. Analogous effects are expected for surfaces of AIII–BV...