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

•The forming gas (FG) annealing results in a significantly reduction of surface native oxide whereby the amount of Ga–O bonds is decreased demonstrated by the X-ray photoelectron spectra. Hydrogen atoms in H2 can react with oxygen atoms in the native oxide layer and remove the oxygen to form a surface with oxygen vacancies. Nitrogen molecules in FG can provide nitrogen atoms to fill up these vacancies. Consequently, the removed native oxide layer during FG annealing leads to the formation of a new nitridation layer on the surface.•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 (fT/fmax) of 165/165 GHz are achieved by the 50-nm InAlN/GaN HEMT annealing by FG H2/N2 on Si substrate.