High vertical breakdown strength with low specific on-resistance in AlGaN/AlN/GaN HEMTs on silicon

Off-state and vertical breakdown characteristics of AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) on high-resistivity (HR)-Si substrate were investigated and analysed. Three-terminal off-state breakdown (BVgd) was measured as a function of gate-drain spacing (L-gd). The saturation of BVgd with L-gd is because of increased gate leakage current. HEMTs with L-gd = 6 mu m exhibited a specific onresistance R-DS[ON] of 0.45 m Omega cm(2). The figure of merit (FOM = BVgd2/R-DS[ON]) is as high as 2.0 x 10(8) V-2 Omega(-1) cm(2), the highest among the reported values for GaN HEMTs on Si substrate. A vertical breakdown of similar to 1000 V was observed on 1.2 mu m thick buffer GaN/AlN grown on Si substrate. The occurrence of high breakdown voltage is due to the high quality of GaN/AlN buffer layers on Si substrate with reduced threading dislocations which has been confirmed by transmission electron microscopy (TEM). This indicates that the AlGaN/AlN/GaN HEMT with 1.2 mu m thick GaN/AlN buffer on Si substrate is promising candidate for high-power and highspeed switching device applications. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim