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

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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 σ₁ (H) and imaginary σ₂ (H) components of the high-frequency conductivity have been determined. Analysis of the σ₁ to σ₂ 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 σ₁ 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.