Improved electrical performance of InAlN/GaN high electron mobility transistors with forming gas annealing

The surface electronic states and defects of gallium nitride based high-electron-mobility transistors (HEMTs) play a critical role affecting channel electron density, electron mobility, leakage current, radio frequency (RF) power output and power added efficiency of devices. This article demonstrates the improved surface properties of InAlN/GaN HEMTs through forming gas (FG) annealing, resulting in a significantly improved electrical properties. The X-ray photoelectron spectra reveals a reduction of surface native oxide after FG H₂/N₂ annealing whereby the amount of Ga–O bonds is decreased. Compared with N₂ annealing, an on-resistance of 1.68 Ω·mm, a subthreshold swing of 118 mV/dec, a transconductance peak of 513 mS/mm, a gate diode breakdown voltage of surpassing 42 V, and a high current/power gain cutoff frequency (f_T/f_max) of 165/165 GHz are achieved by the 50-nm InAlN/GaN HEMT on Si substrate.