GaN MESFETs on (111)Si substrate grown by MOCVD

A GaN metal-semiconductor field-effect transistor (MESFET) has been grown on (111) Si substrate by metalorganic chemical vapour deposition using Al_0.27Ga_0.73N/AlN intermediate layers. The device showed a maximum extrinsic transconductance 25 mS/mm and a drain-source current 169 mA/nm with a complete pinch-off for the 2.5 μm gate-length. The Al_0.27Ga_0.73N/AlN intermediate layers were effective in obtaining a mirror-like surface morphology and a high-resistive undoped GaN layer beneath a channel layer. The GaN MESFET on Si also exhibited no self-heating effects (drain-source current reduction) under high-power conditions. Which results from the better thermal properties of Si than those of sapphire