Acoustoelectric effects in very high-mobility $p$-SiGe/Ge/SiGe heterostructure

TL;DR

This paper investigates the acoustoelectric effects, including SAW attenuation and velocity, in a high-mobility p-SiGe/Ge/SiGe heterostructure at low temperatures and high magnetic fields, revealing quantum oscillations and energy relaxation properties.

Contribution

It provides the first detailed measurement of acoustoelectric effects in a high-mobility p-SiGe/Ge/SiGe heterostructure, including quantum oscillations and energy relaxation times, without using electric contacts.

Findings

Observation of Shubnikov-de Haas-like oscillations in SAW attenuation and velocity

Measurement of hole density, mobility, and effective mass

Determination of energy relaxation time and deformation potential constant

Abstract

Measurement results of the acoustoelectric effects (surface acoustic waves (SAW) attenuation and velocity) in a high-mobility $p$-SiGe/Ge/SiGe structure are presented. The structure was LEPECVD grown with a two dimensional (2D) channel buried in the strained Ge layer. The measurements were performed as a function of temperature (1.5 - 4.2 K) and magnetic field (up to 8.4 T) at different SAW intensities at frequencies 28 and 87 MHz. Shubnikov-de Haas-like oscillations of both SAW attenuation and the velocity change have been observed. Hole density and mobility, effective mass, quantum and transport relaxation times, as well as the Dingle temperature were measured with a method free of electric contacts. The effect of heating of the 2D hole gas by the electric field of the SAW was investigated. Energy relaxation time $\tau_{\varepsilon}$ and the deformation potential constant determined.