Narrow Results

We analyze steady-state and transient electron transport in the group III-nitride materials at high and ultra-high electric fields for different electron concentration regimes. At high electron concentrations where the electron distribution function assumes a shifted Maxwellian, we investigate different time-dependent transient transport regimes through the phase-plane anyalysis. Unexpected electron heating pattern is observed during the velocity overshoot process with a moderate electron temperature near the peak velocity followed by rapid increase in the deceleration period. For short nitride diodes, spacecharge limited transport is considered by taking into account the self-consistent field. In this case, the overshoot is weaker and the electron heating in the region of the peak velocity is greater than that found for time-dependent problem. The transient processes are extended to sufficiently larger distances as well. When the electron concentration is small, we propose a model which accounts the main features of injected electrons in a short device with high fields. The electron velocity distribution over the device is found as a function of the field. It is demonstrated that in high fields the electrons are characterized by the extreme distribution function with the population inversion.

AlGaN thin films and Schottky barrier Al_0.4Ga_0.6N diodes exhibit generation-recombination (GR) noise with activation energies of 0.8 - 1 eV. GR noise in AlGaN/GaN Heterostructure Field Effect transistors (HFETs) corresponds to activation energies in the range from 1 - 3 meV to 1 eV. No GR noise is observed in thin doped GaN films and GaN MESFETs. GR noise with the largest reported activation energy of 1.6 eV was measured in AlGaN/InGaN/GaN Double Heterostmcture Field Effect Transistors (DHFETs). Local levels responsible for the GR noise in HFETs and DHFETs might be located in AlGaN barrier layers.