Fast and ultrafast dissipation and fluctuations in two-dimensional channels for nitride and arsenide FETs

Abstract

Microwave noise technique is applied to study fast and ultrafast correlations in nitride and arsenide heterostructures containing a two-dimensional electron gas subjected to a strong electric field applied in the plane of electron confinement. The main attention is paid to experimental investigation of electron energy dissipation, hot phonons, and high-energy electrons shared by the adjacent layers (real-space transfer). The typical experimental values for the time of electron energy relaxation range from several picoseconds at low electric fields and low ambient temperatures to hundreds of femtoseconds at a high field. The measured dependence of the electron energy relaxation time on the bias is compared with those obtained through Monte Carlo simulation for different models. An essential contribution due to hot phonons and electron gas degeneracy is evidenced. Dependence of hot-phonon temperature on the electron temperature is deduced from the experimental results on the microwave noise and the dissipated power. The adjacent layers share the high-energy electrons unless the heterojunction barrier is high. Random transitions between the confined and the shared states cause microwave noise. The relaxation time of the occupancy fluctuations is estimated from the measured spectral intensity of current fluctuations. Hot phonons are found to reduce the threshold field for this noise source. The experimental data on AlGaN/GaN, AlGaAs/GaAs and AlInAs/GaInAs/AlInAs are compared.