Buffer Thickness Contribution to Suppress Vertical Leakage Current With High Breakdown Field (2.3 MV/cm) for GaN on Si

Vertical breakdown studies on AlGaN/GaN high-electron-mobility transistors (HEMTs) grown by metal-organic chemical vapor deposition (MOCVD) on a silicon substrate are studied to analyze the breakdown dependence with regard to i-GaN thickness (T-GaN) and buffer thickness (T-Buf). A high breakdown field (E-c) of 2.3 MV/cm was observed for MOCVD-grown epilayers of total thickness of 5.5 mu m on Si. Increasing T-Buf is more significant than T-GaN toward controlling the vertical leakage and demonstrates a high breakdown. For transistor operation at high voltages, GaN layers grown on thick buffers are highly resistive to the flow of leakage currents. A high figure of merit ((BVRd-ON)-R-2/) of 5.4 x 10(8) V-2 . Omega(-1) . cm(-2) was observed for an AlGaN/GaN HEMT grown on Si using a thick buffer.