Surface Acoustic Waves probe of the p-type Si/SiGe heterostructures

Abstract

The surface acoustic wave (SAWs) attenuation coefficient $Γ$ and the velocity change $ΔV /V$ were measured for $p$-type Si/SiGe heterostructures in the temperature range 0.7 - 1.6 K as a function of external magnetic field $H$ up to 7 T and in the frequency range 30-300 MHz in the hole Si/SiGe heterostructures. Oscillations of $Γ$ (H) and $ΔV /V$ (H) in a magnetic field were observed. Both real $σ_1$ (H) and imaginary $σ_2$ (H) components of the high-frequency conductivity have been determined. Analysis of the $σ_1$ to $σ_2$ ratio allows the carrier localization to be followed as a function of temperature and magnetic field. At T=0.7 K the variation of $Γ$, $ΔV /V$ and $σ_1$ with SAW intensity have been studied and could be attributed to 2DHG heating by the SAW electric field. The energy relaxation time is found to be dominated by scattering at the deformation potential of the acoustic phonons with weak screening.