High-Frequency AlGaN/GaN High-Electron-Mobility Transistors with Regrown Ohmic Contacts by Metal-Organic Chemical Vapor Deposition

Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15 Ω?mm is obtained. It is found that the sidewall obliquity near the regrown interface induced by the plasma dry etching has great influence on the total contact resistance. The fabricated device with a 100-nm T-shaped gate demonstrates a maximum drain current density of 0.95 A/mm at V_gs=1 V and a maximum peak extrinsic transcondutance G_m of 216 mS/mm. Moreover, a current gain cut-off frequency f_T of 115 GHz and a maximum oscillation frequency f_max of 127 GHz are achieved.