Skip to Main Content
In this letter, we present the device characteristics of AlGaN/GaN heterostructures grown on 4-in Si using various buffer thicknesses (TBuf). The transmission electron microscopic image confirms a low dislocation density (9.7 × 107 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 (Lgd) exceeding 15 μm. However, an increase in TBuf 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 · cm2. A figure of merit (FOM = BV2/Ron) of 2.6 × 108 V2 · Ω-1 · cm-2 was observed for our devices, which is the highest for an AlGaN/GaN HEMT grown on Si.