THE EFFECT OF AN INTENSE TERAHERTZ IRRADIATION ON ELECTRON-TRANSPORT IN 2-DIMENSIONAL SEMICONDUCTORS

We study theoretically the electron transport in GaAs-based quasi-two- dimensional systems under the influence,of an intense terahertz electr omagnetic irradiation, using a balance equation approach in which the slowly varying part of the centre-of-mass velocity is distinguished fr om the rapidly oscillating part of it. Electron scatterings by charged impurities, and acoustic and polar optical phonons are considered and up to as many as [n] = 60 multiphoton channels are taken into account . The carrier mobility and the electron temperature of a typical GaAs quantum well system are calculated in the limit of small de drift velo city (small de field) as functions of the radiation-field strength for various frequencies in the range from 1 to 10 THz at lattice temperat ure T = 10, 77, 150 and 300 K. We find that at low lattice temperature (T = 10 K), de mobility decreases monotonically with increasing stren gth of the radiation field, and lower frequency generally has a strong er effect in suppressing the mobility, in agreement with the experimen tal observation. At room temperature, on the other hand, the present t heory predicts an enhancement of the de mobility due to irradiation wi th a THz field.