Microwave Noise and Fast/Ultrafast Electronic Processes in Nitride 2DEG Channels

Microwave noise technique is applied to study ultrafast correlations in AlGaN/GaN and AlN/GaN two-dimensional electron gas (2DEG) channels subjected to a strong electric field applied in the plane of electron confinement. The experimental data are discussed in terms of hot-electron- energy dissipation on phonons, longitudinal-optical (LO) phonon conversion into other phonon modes, and hot-electron deconfinement. At high electric fields, the hot-electron energy relaxation is limited by the LO-phonon conversion. The LO-phonon conversion lifetime is estimated to be 350 fs in AlGaN/GaN channel. The lifetime is a useful parameter for extrapolation of hot-electron temperature beyond the field range where it is available from microwave noise experiments. The extrapolated hot-electron temperature is used to discuss hot-electron deconfinement noise.