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

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 nonoxidiz ed intrinsic base of the fabricated collector-up MBT on a sapphire substrat e was estimated to be 2-3 nm. Although the MBT showed large leakage, subtra ction of the leakage from collector cut-rent revealed that the transistor h ad a very large small-signal direct current (dc) current gain of 87 dB and a de power gain of 50 dB. This indicates that the GaN-based MBT is a possib le candidate for microwave and millimeterwave amplifiers as well as for hig h-speed integrated circuits used in optical fiber communication system. (C) 2000 American Institute of Physics. [S0003-6951(00)04231-5].