Patent ID: 9076906
Filing Date: 2015-07-07
Classification: H01L,Y02E

Abstract:
1. A hetero junction bipolar phototransistor, comprising: a photo-absorption layer formed of a first conductivity type semiconductor layer, and a collector operating as a barrier layer, a base layer, and an emitter layer, which are in direct contact with each other in sequence on the photo-absorption layer, wherein said photo-absorption layer, said collector operating as the barrier layer, said base layer and said emitter layer forming a first mesa structure, and an emitter contact layer forming a second mesa structure form the phototransistor; said photo-absorption layer comprises a semiconductor layer with a narrow bandgap corresponding to a light-sensing wavelength of the phototransistor wherein an energy level in a conduction band edge of the photo-absorption layer is lower than an energy level in a conduction band edge of the collector operating as the barrier layer, and an energy level in a valence band edge of the photo-absorption layer is equal to or less than an energy level of a valence band edge of the collector operating as the barrier layer; said collector operating as the barrier layer essentially consists of a semiconductor layer of single material composition with a relatively wider bandgap than a bandgap of said photo-absorption layer where the energy level in the conduction band edge is higher than the energy level of said photo-absorption layer in the conduction band edge, and the energy level in the valence band edge is equal to or higher than the energy level of said photo-absorption layer in the valence band edge; said base layer formed on said collector operating as the barrier layer has an energy level in a conduction band edge which is equal to or higher than the energy level in the conduction band edge of the collector operating as the barrier layer; said emitter layer formed on the base layer has a relatively wide bandgap as compared to said base layer, and an energy level in a valence band of the emitter layer is lower than an energy level in a valence band of the base layer; and said photo-absorption layer comprises InGaAs, and said collector operating as the barrier layer comprises InGaAsPSb, and said base layer comprises InGaAsPSb.