Breakdown mechanism in AlGaN/GaN HEMTs on Si substrate

AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates have attracted a great interest for power electronics applications. Despite the low cost of the Si substrate, the breakdown voltage (V_bk) of AlGaN/GaN HEMTs grown on Si (less than 600 V for 2 μm total nitride epilayer) is much lower than that grown on SiC (1.9 kV for 2 μm total epi-layer). Although several approaches have been reported to improve V_bk, the breakdown mechanism in these transistors is still not well understood. This paper studies for the first time the breakdown mechanism in AlGaN/GaN HEMTs on Si substrates. In addition, by transferring the AlGaN/GaN HEMTs grown on Si to a glass wafer, we have achieved devices with V_bk in excess of 1.45 kV and specific on-resistance of 5.3 mΩ.cm².