Power loss by two-dimensional holes in coherently strained Ge0.2Si0.8/Si heterostructures: Evidence for weak screening

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Abstract
We have used the hot‐carrier Shubnikov–de Haas effect to measure the power loss by hot two‐dimensional holes in coherently strained Ge0.2Si0.8/Si heterostructures. The measured power loss versus carrier temperature data are best described by the two‐dimensional formalism of P. J. Price [J. Appl. Phys. 5 3, 6864 (1982)] assuming weak screening. Excellent agreement with experiment is obtained only if scattering of the acoustic mode phonons by both the deformation potential and the piezoelectric coupling mechanisms are considered. We are therefore able to deduce a value for the piezoelectric constant for Ge0.2Si0.8 which is approximately 35% of that for InAs (e2pz≊0.22×108 dyne/cm2). In light of the fact that charge transfer effects are expected to be small in bulk (unstrained) GexSi1−x, the present observations are indicative of either a large strain induced change in ionicity or of scattering of acoustic phonons from ordered domains via the piezoelectric mechanism.