ESTIMATION OF ELECTRON ENERGY RELAXATION TIME IN 2DEG CHANNELS FROM TRANSVERSE AND LONGITUDINAL NOISE

Abstract

Microwave noise is investigated in heterostructures subjected to an electric field applied parallel to the interfaces. The longitudinal and transverse noise temperatures are measured and simulated in the plane of electron confinement in the directions perpendicular and parallel to the electric field. Monte Carlo simulation is performed for a subcritically doped InAlAs/InGaAs/InAlAs heterostructure containing a two-dimensional electron gas in a single channel. The simulated longitudinal noise temperature is found to be nearly the same as the transverse one in the field range where the interwell transfer of hot electrons is not important. The longitudinal noise temperature exceeds the transverse one considerably in a supercritically doped InAlAs/InGaAs/InAlAs/InP heterostructure containing three separate quantum-well channels, each accommodating a two-dimensional electron gas at equilibrium. The observed strong planar anisotropy is ascribed to the channel occupancy fluctuations caused by the interwell transfer of equilibrium electrons. A possibility to estimate energy relaxation time from the transverse and the longitudinal microwave noise measurements is discussed.