Monte Carlo study of terahertz generation from streaming distribution of two-dimensional electrons in a GaN quantum well

Abstract

We study terahertz (THz) generation from anisotropic streaming distribution of a two-dimensional electron gas (2DEG) in a GaN/AlGaN quantum well using the ensemble Monte Carlo method. Under proper electric fields, electrons do not have enough energy for intersubband and intervalley transitions. They make nearly cyclic motion in momentum space within the first subband, which gives rise to a spindle-shaped electron distribution. This effect is improved due to large polar optical phonon energy, strong electron–phonon interaction and much sharper increase of the polar optical phonon emission rate in GaN 2DEG. We demonstrate that electrons show dynamic negative differential mobility at the transit-time frequency and its harmonics at low temperatures due to this cyclic motion. The resonant frequency can be tuned by simply varying the applied electric field. We may thus use this effect to develop voltage-tunable THz masers.