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 μm on Si. Increasing T_Buf is more significant than TGaN toward controlling the vertical leak age 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 (BV²/R_d.ON) of 5.4 × 10⁸ V² · Ω^-1· cm^-2 was observed for an AlGaN/GaN HEMT grown on Si using a thick buffer.