AlGaN/GaN/InGaN/GaN DH-HEMTs with an InGaN notch for enhanced carrier confinement

Abstract

We report an AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) with high-mobility two-dimensional electron gas (2-DEG) and reduced buffer leakage. The device features a 3-nm thin In/sub x/Ga/sub 1-x/N(x=0.1) layer inserted into the conventional AlGaN/GaN HEMT structure. Assisted by the InGaN layers polarization field that is opposite to that in the AlGaN layer, an additional potential barrier is introduced between the 2-DEG channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. For a sample grown on sapphire substrate with MOCVD-grown GaN buffer, a 2-DEG mobility of around 1300 cm/sup 2//V/spl middot/s and a sheet resistance of 420 /spl Omega//sq were obtained on this new DH-HEMT structure at room temperature. A peak transconductance of 230 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 14.5 GHz, and a peak power gain cutoff frequency (f/sub max/) of 45.4 GHz were achieved on a 1/spl times/100 /spl mu/m device. The off-state source-drain leakage current is as low as /spl sim/5 /spl mu/ A/mm at V/sub DS/=10 V. For the devices on sapphire substrate, maximum power density of 3.4 W/mm and PAE of 41% were obtained at 2 GHz.