Phototransistor of the type having an emitter-base heterojunction

摘要

A phototransistor comprising a substrate (9), a collector layer (2), a base layer (3), and an emitter layer (4) is disclosed. The base layer (3) is of a first composite III-V semiconductor material with a first type of doping and the emitter layer (4) is of a second composite III-V semiconductor material. A diffusion well (6), of the first type of doping extends on a main part of the emitter layer (4) down to the base layer. The remaining part of the emitter layer (4) is of a second type of doping. The main part of the emitter layer (4) has an area at least 100 times larger than the area of the remaining part. A contact layer with the second type of doping is deposited on the remaining part of the emitter layer (4) with an emitter contact on the contact layer, and a base contact on an extremity of the diffusion well (6). Such a phototransistor thus comprises a heterojunction transistor under the emitter contact and a homojunction photodiode under the diffusion well (6) , and the diffusion well (6) is transparent in most of its thickness to light radiation to be detected.