Optimization of AlGaN/GaN HEMT Schottky contact for microwave applications

Platinum (Pt/Ti/Pt/Au) gate contact of AlGaN/GaN high electron mobility transistor (HEMT) with low gate leakage current is demonstrated. For comparison, Titanium (Ti/Al/Ti) gate devices are also fabricated using the same process flow except the gate topology which is double T-shaped gate for Ti/Al/Ti. Comparable extrinsic transconductance is obtained for the two kinds of devices ranging 400 mS/mm. At gate voltage of -3 V, typical gate leakage current is found to be as low as 1 μA for a 2×50×0.110 μm² Pt-gate device. This value is 10 times lower than that of Ti/Al/Ti-gate device measured under the same bias conditions. RF measurement demonstrates F_MAX/F_T of 170/80 and 200/70 on devices based on Pt/Ti/Pt/Au and Ti/Al/Ti Schottky contacts respectively. These results indicate that platinum could be a promising gate metallization candidate for high-performance microwave power AlGaN/GaN HEMTs on Si substrate.