Abstract
We examine the frequency dependence of the energy relaxation of hot electrons under the influence of an intense oscillatingelectric field of terahertz frequency. The calculated energy-loss rates in a GaAs/AlGaAs heterojunction and two GaAs-based quantum wells exhibit a frequency behavior quite different from that of the widely used Kogan formula. Their ratio shows an unexpected peak at around 0.5–0.6 THz, with a height about 3–10 times of its low-frequency value. This remarkable resonance is a unique indication of the role of the Doppler shift of the phonon frequency.