Highly scaled graded channel GaN HEMT with peak drain current of 2.48 A/mm

Abstract

The dc and high frequency performances of Al composition Graded Channel AlGaN/GaN high electron mobility transistor on GaN substrate was investigated and compared with Conventional AlGaN/GaN HEMT. The high frequency characteristics were measured on both the AlGaN/GaN HEMTs scaling the gate length from 800 nm to 50 nm. The 50 nm gate length Graded Channel AlGaN/GaN HEMT exhibited the highest drain current of 2.48 A/mm and transconductance of 0.32 S/mm respectively at a drain voltage of VD = 10 V. Also the transconductance curve of the Graded Channel HEMT is flatter than that of conventional GaN HEMT. The flatter transconductance curve reduces the power gain roll off in Graded Channel HEMT and thus gives improved performance in terms of device linearity. The current gain cutoff frequency fT = 126.5 GHz was obtained for the Graded Channel HEMT at a gate length of 50 nm. This accounts to 61.6% increase in fT when compared to conventional GaN HEMT at the same gate length of 50 nm.