Admittance spectroscopy of Si Si1-x Gex Si quantum well systems: Experiment and theory

We present a combined experimental and theoretical study on the admittance spectroscopy of Si Si1-x Gex Si single quantum well structures. Experimentally, the admittance spectra are measured for Si1-x Gex -based two-dimensional hole gas systems. The dependence of the spectra on width of the quantum well and on content of Ge is investigated. Theoretically, in conjunction with the measurements we develop a simple and systematic approach to calculate the conductance and capacitance on the basis of a Boltzmann equation in which the emission rate induced by hole-phonon scattering is considered. We compare the theoretical results with those obtained experimentally and find that our model calculation can reproduce nicely the experimental findings.