Abstract: A non-micro-air-bridge InP-based heterojunction bipolar transistor (HBT) is fabricated.A very small emitter side etching (＜100nm) is developed and makes a submicron InP-based HBT possible.The current gain cutoff frequency is as high as 238GHz for the submicron HBT with an emitter area of 0.8μm×15μm due to the reduction of emitter width.A base-collector over-etching technology is developed,resulting in a reduction of base-collector junction area and an increase in the maximum oscillation frequency.A very high Kirk current density of 3.1mA/μm2 is obtained.To the best of our knowledge,the current gain cutoff frequency is the highest among three-terminal devices in China and the Kirk current density is also the highest in HBTs reported in China.This is very helpful for the application of HBTs in ultra high-speed circuits.

Key words: InP, heterojunction bipolar transistor, planarization, high frequency