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

TL;DR

This study uses surface acoustic waves to investigate the electrical and physical properties of p-type Si/SiGe heterostructures at very low temperatures, revealing carrier localization, conductivity behavior, and energy relaxation mechanisms.

Contribution

It provides new insights into the high-frequency conductivity and carrier dynamics in p-type Si/SiGe heterostructures using SAWs at cryogenic temperatures.

Findings

Observation of oscillations in SAW attenuation and velocity change with magnetic field.

Determination of real and imaginary components of high-frequency conductivity.

Identification of energy relaxation dominated by scattering at deformation potential of acoustic phonons.

Abstract

The surface acoustic wave (SAWs) attenuation coefficient $\Gamma$ and the velocity change $\Delta V /V$ 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 $\Gamma$ (H) and $\Delta V /V$ (H) in a magnetic field were observed. Both real $\sigma_1$ (H) and imaginary $\sigma_2$ (H) components of the high-frequency conductivity have been determined. Analysis of the $\sigma_1$ to $\sigma_2$ ratio allows the carrier localization to be followed as a function of temperature and magnetic field. At T=0.7 K the variation of $\Gamma$, $\Delta V /V$ and $\sigma_1$ 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.