Effects of notch structures on DC and RF performances of AlGaN/GaN high electron mobility transistors*

The effects of various notch structures on direct current (DC) and radio frequency (RF) performances of AlGaN/GaN high electron mobility transistors (HEMTs) are analyzed. The AlGaN/GaN HEMTs, each with a 0.8-mu m gate length, 50-mu m gate width, and 3-mu m source-drain distance in various notch structures at the AlGaN/GaN barrier layer, are manufactured to achieve the desired DC and RF characteristics. The maximum drain current (I (ds,max)), pinch-off voltage (V (th)), maximum transconductance (g (m)), gate voltage swing (GVS), subthreshold current, gate leakage current, pulsed I-V characteristics, breakdown voltage, cut-off frequency (f (T)), and maximum oscillation frequency (f (max)) are investigated. The results show that the double-notch structure HEMT has a 30% improvement of gate voltage swing, a 42.2% improvement of breakdown voltage, and a 9% improvement of cut-off frequency compared with the conventional HEMT. The notch structure also has a good suppression of the current collapse.