1.4-kV Breakdown Voltage for AlGaN/GaN High-Electron-Mobility Transistors on Silicon Substrate

In this letter, we present the device characteristics of AlGaN/GaN heterostructures grown on 4-in Si using various buffer thicknesses (T Buf ). The transmission electron microscopic image confirms a low dislocation density (9.7 × 10 7 cm -2 ) for our epilayers grown using thick buffer layers. An increase in mobility and a decrease in sheet resistance of these samples were observed owing to improved crystal quality for GaN on thick buffer. High electron-mobility transistors (HEMTs) tested for three-terminal off breakdown voltage (3TBV ) show signs of breakdown voltage saturation for gate-drain length (L gd ) exceeding 15 μm. However, an increase in T Buf causes a drastic increase in 3TBV , and a high 3TBV of 1.4 kV was observed with a specific on-resistance of 9.6 mΩ · cm 2 . A figure of merit (FOM = BV 2 /R on ) of 2.6 × 10 8 V 2 · Ω -1 · cm -2 was observed for our devices, which is the highest for an AlGaN/GaN HEMT grown on Si.