Full band Monte Carlo comparison of wurtzite and zincblende phase GaN MESFETs

The output characteristics, cutoff frequency, breakdown voltage and the tra nsconductance of wurtzite and zincblende phase GaN MESFETs have been calcul ated using a self-consistent, full band Monte Carlo simulation. It is Found that the calculated breakdown voltage for the wurtzite device is considera bly higher than that calculated for a comparable GaN zincblende phase devic e. The zincblende device is calculated to have a higher transconductance an d cutoff frequency than the wurtzite device, The higher breakdown voltage o f the wurtzite phase device is attributed to the higher density of electron ic states for this phase compared to the zincblende phase. The higher cutof f frequency and transconductance of the zincblende phase GaN device is attr ibuted to more appreciable electron velocity overshoot for this phase compa red to that for the wurtzite phase. The maximum cutoff frequency and transc onductance of a 0.1 mum gate-length zincblende GaN MESFET are calculated to be 220GHz and 210 mS/mm, respectively. The corresponding quantities for th e wurtzite GaN device are calculated to be 160GHz and 158 mS/mm.