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Electron relaxtion after an instantaneous application of a dc electric field ranging from 10 V/cm to 1 kV/cm is studied numerically by a many‐particle Monte Carlo method. The model takes into account polar optical, acoustic, and impurity scattering in the nonparabolic central valley. In the limited range of doping, electric field, and temperature the electron mean energy and drift velocity oscillate. The oscillation frequency is nearly proportional to the applied electric field (approximately 35 GHz at 60 V/cm). The oscillations are associated with a shuttle‐type electron motion in the Debye sphere of k‐space they are not heavely damped if the electron runaway is favoured inside and restrained outside the Debye sphere.

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The intrasubband electron-polar optical phonon scattering rates for interface and confined phonons are calculated. The AIAslGaAslAIAs double heterostructures with independent confinement of electrons and phonons as well as structures containing a phonon wail (a phonon-reflecting barrier transparent to electrons) embedded in an electron quantum well (QW) are considered. it is shown that, because of the independent electron and phonon confinement in the double heterostructure, the scattering rate is lower than that obtained in the case of electron confinement alone. The total scattering rate by confined and interface phonons in the QW with a phonon wall is reduced significantly a s compared with the rate of confined electron scattering by bulk phonons. Thus, the phonon wall within the electron QW is a powerful means of reducing electron scattering and enhancing, correspondingly. the electron mobility in two-dimensional (ZD) heterostructures.

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