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We investigate acoustic deformation potential scattering in Al$\sb{\rm x}$Ga$\sb{1-\rm x}$As/GaAs modulation doped heterojunctions. We review previous measurements of the deformation potential constant Z and discuss the controversy over the discrepancy between the measured value of Z in bulk GaAs and in the heterojunction. By comparing the theory of scattering in bulk GaAs with previously reported measurements of the mobility at 77 K we determine an upper limit for the deformation potential constant of 11 eV.
We experimentally measure the relationship between the electron temperature and the power loss, and we compare our measurements with theory. We conclude, in general agreement with previous measurements in heterojunctions, that a large value of the deformation potential constant (approximately 16 eV) would be necessary to fit the data using a theory of acoustic phonon scattering. In contrast with previously reported studies of acoustic deformation potential scattering in heterojunctions, we do not conclude that earlier measurements of Z in bulk GaAs are in error. Instead, we suggest a number of possible enhancements to the theory which may explain the anomalously large power loss which we observe. Our experiment, unlike previous studies of the mobility, indicates clearly that if an additional scattering mechanism is the cause, then it must be an inelastic mechanism.
We also present a comprehensive theory of the electronic power loss in the heterojunction, including the effects of screening. It is found that screening changes the temperature dependence of the power loss (or the mobility) and that this makes it possible to conclusively observe the effects of screening at low temperatures. Analytical solutions of the power loss equation are presented and the temperature range over which the analytical solution is valid is discussed. It is found that the analytical solutions are valid only at temperatures much lower than previously believed.
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