InGaN/GaN microwave varactors with high Q, high-breakdown voltage and high linearity

Semiconductor varactors are receiving increasing attention because of their potential to provide adaptive and tunable characteristics for the front-end of wireless communication systems, enabling efficient multi-band and software-defined radios. For base-station applications, Q > 100, breakdown voltage > 100 V and OIP3 > 65 dBm are required. The combination of high Q and high-breakdown voltage requires semiconductors with high mobility and high-breakdown electric field [1]; GaN with a mobility of >∼ 500 cm 2 /Vsec and a breakdown electric field of 2.5 MV/cm is a promising candidate. SiC-based varactors have also been recently reported [2]. We have previously demonstrated GaN large-area varactors that achieve high-breakdown voltage. The addition of a thin InGaN surface layer was shown to increase the diode breakdown voltage and reduce the leakage current under high reverse bias [3]. In this work, InGaN/GaN Schottky-diode microwave varactors with Q > 100 at 1 GHz, breakdown voltage > 120 V and OIP3 > 71 dBm are reported. To the best of our knowledge, the combination of Q, voltage handling capability and OIP3 represents advancement from any other reported varactors.