Gate length scaling for Al/sub 0.2/Ga/sub 0.8/N/GaN HJFETs: two-dimensional full band Monte Carlo simulation including polarization effect

Abstract

Two-dimensional self-consistent full band Monte Carlo (FBMC) simulator was developed for electron transport in wurtzite phase AlGaN/GaN heterojunction (HJ) FET. Recessed gate Al/sub 0.2/Ga/sub 0.8/N/GaN HJFET structures with an undoped cap layer were simulated, where the spontaneous and piezoelectric polarization effects were taken into account. The polarization effect was shown to not only increase the current density, but also improve the carrier confinement, and hence improve the transconductance. An off-state drain breakdown voltage (BV/sub ds/) of 300 V and a maximum linear output power (P/sub max/) of 46 W/mm were predicted for a 0.9-/spl mu/m gate device. For a 0.1-/spl mu/m gate device, 60 V BV/sub ds/, 20 W/mm P/sub max/, and 160 GHz current-gain cutoff frequency were predicted. Although there is considerable uncertainty due to lack of information on the band structure, scattering rates, and surface conditions, the present results indicate a wide margin for improvements over current performance of AlGaN/GaN HJFETs in the future. To our knowledge, this is the first report on the FBMC simulation for AlGaN/GaN HJFETs.