Low-Temperature Ohmic Contact Formation in GaN High Electron Mobility Transistors Using Microwave Annealing

In this letter, a low-temperature microwave annealing (MWA) method is first reported for the formation of ohmic contact to AlGaN/GaN high electron mobility transistors (HEMTs). Compared with the traditional GaN devices annealed by rapid thermal annealing (RTA), MWA-HEMTs can achieve a low ohmic contact resistance with much smoother surface of ohmic contacts. The spike mechanism is observed in our ohmic contact annealed by microwave under a low-temperature condition. Besides, MWA-HEMTs have higher $I_{\mathrm{{\scriptscriptstyle ON}}}/I_{\mathrm{{\scriptscriptstyle OFF}}}$ ratio and lower gate leakage current than the fabricated RTA-HEMTs in this letter.