High RF Performance AlGaN/GaN HEMT Fabricated by Recess-Arrayed Ohmic Contact Technology

In this letter, a high-performance gate-recessed AlGaN/GaN high electron mobility transistor (HEMT) fabricated by the recess-arrayed ohmic contact technology is presented. An array of square columns was etched in the ohmic region, using Ti/Al/Ni/Au metal deposition and rapid annealing to fabricate a low-resistance ohmic contact. By using the transmission line method measurement, an ohmic contact resistance (R-c) of 0.12 Omega . mm is measured, which is 70% lower than that of the reference device. The patterned ohmic contact HEMT (POC HEMT) exhibits the saturation current of 1130 mA/mm at V-ds = 10 V and V-gs = 1 V, with a shift of the knee voltage from 6 V to 3 V. The RF measurement shows the power-added efficiency (PAE) of 71.6% at 5 GHz. After the third harmonic tuning, the PAE of 85.2% and the corresponding power density of 11.2W/mm and power gain of 16.9 dB are obtained. According to the achieved results, the recess-arrayed ohmic contact processed GaN HEMT has a great potential for high RF efficiency and power applications.