Improved RF power performance of InAlN/GaN HEMT by optimizing rapid thermal annealing process for high-performance low-voltage terminal applications

Abstract

In this work, improved RF power performance of InAlN/GaN HEMT is achieved by optimizing rapid thermal annealing (RTA) process for high performance low voltage terminal applications. By optimizing the RTA temperature and time, the optimal annealing condition is found to enable low parasitic resistance and thus high performance device. Besides, comparing with the non-optimized RTA HEMT, the optimized one demonstrates smoother ohmic metal surface morphology and better heterojunction quality including the less degraded heterojunction sheet resistance and clearer heterojunction interfaces as well as negligible material out-diffusion from the barrier to the channel and buffer. Benefitting from the lowered parasitic resistance, improved maximum output current density of 2279 mA/mm and higher peak extrinsic transconductance of 526 mS/mm are obtained for the optimized RTA HEMT. In addition, attributed to the superior heterojunction quality, the optimized HEMT shows reduced off-state leakage current of 7 × 10-3 mA/mm and suppressed current collapse of only 4%, compared with those of 1 × 10-1 mA/mm and 15% for the non-optimized one. At 8 GHz and VDS of 6 V, significantly improved power-added-efficiency of 62% and output power density of 0.71 W/mm are achieved for the optimized HEMT, as the result of the improvement in output current, knee voltage, off-state leakage current and current collapse, which reveals the large advantage of the optimized RTA HEMT in high performance low voltage terminal applications.