Transient electron transport in wurtzite GaN, InN, and AlN

Transient electron transport and velocity overshoot in wurtzite GaN, InN, a nd AlN are examined and compared with that which occurs in GaAs. For all ma terials, we find that electron velocity overshoot only occurs when the elec tric field is increased to a value above a certain critical field, unique t o each material. This critical field is strongly dependent on the material, about 4 kV/cm for the case of GaAs but much higher for the III-nitride sem iconductors: 140 kV/cm for GaN, 65 kV/cm for InN, and 450 kV/cm for AlN. We find that InN exhibits the highest peak overshoot velocity and that this v elocity overshoot lasts over the longest distances when compared with GaN a nd AlN. Finally, using a one-dimensional energy-momentum balance approach, a simple model is used to estimate the cutoff frequency performance of nitr ide based heterojunction field effect transistors (HFETs) and a comparison is made to recently fabricated AlGaN/GaN HFETs. (C) 1999 American Institute of Physics. [S0021-8979(99)04110-9].