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 x 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 mu m. 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 m Omega . cm(2). A figure of merit (FOM = BV2/R-on) of 2.6 x 10(8) V-2 . Omega(-1) . cm(-2) was observed for our devices, which is the highest for an AlGaN/GaN HEMT grown on Si.