| 摘要 |
PURPOSE:To suppress a dark current in a phototransistor by increasing the forbidden band-width of emitter and base layers larger than that of a collector layer. CONSTITUTION:An emitter 11 is formed of n type AlxGa1-xAs, a bsse 21 is formed of p type AlyGa1-yAs, a collector 31 is formed of n type GaAs, a substrate 51 is formed of n type GaAs, and a depletion layer 41 extends to the region 31. Since it is formed of a material having forbidden band width larger than the collector 31 at the emitter 11 and base 21, and the amplifying region has large forbidden band with as compared with the photoelectric conversion region in the phototransistor. Since the thermal excitation of electrons and holes is small in the region having large forbidden band-width, a dark current generated in the amplifying region can be suppressed to small degree to be ignored as compared with the unavoidable dark current generated in the photoelectric conversion region in the transistor. |
