Gain-Enhanced InGaAs–InP Heterojunction Phototransistor With Zn-Doped Mesa Sidewall

A gain-enhanced InGaAs-InP heterojunction phototransistor (GE-HPT) with a Zn-doped mesa sidewall designed to reduce both base-emitter recombination currents and base-collector dark currents is realized. The developed GE-HPT has an optical conversion efficiency as large as 24 kA/W at an incident optical power of 29 nW and a wavelength of 1.55 mum, which is the highest gain yet reported in HPTs. The measured dark current in the base-collector junction is comparable to that of planar-type PIN photodiodes. The high gain and low dark current characteristics of the phototransistors make them promising for use in a weak light detection system.