GaN/W/W-oxide metal base transistor with very large current gain and power gain

We demonstrate a GaN/W/W-oxide metal base transistor (MBT) whose collector is formed by oxidizing the intrinsic W base. The thickness of the nonoxidized intrinsic base of the fabricated collector-up MBT on a sapphire substrate was estimated to be 2–3 nm. Although the MBT showed large leakage, subtraction of the leakage from collector current revealed that the transistor had a very large small-signal direct current (dc) current gain of 87 dB and a dc power gain of 50 dB. This indicates that the GaN-based MBT is a possible candidate for microwave and millimeterwave amplifiers as well as for high-speed integrated circuits used in optical fiber communication system.