Abstract: Large-scale Heterojunction Bipolar Transistors were fabricated by using AlGaInP/GaAs HBT material grown by MOCVD. DC characteristics of AlGaInP/GaAs SHBT and AlGaInP/GaAs DHBT were studied. In addition, the collector-emitter offset voltages of AlGaInP/GaAs HBT were investigated, and several electrical factors affecting the offset voltage were discussed in detail. The results show that the collector-emitter offset voltages of AlGaInP/GaAs HBT are closely related to base current. And the collector-emitter offset voltage of AlGaInP/GaAs HBT can be decreased greatly by adopted wide emitter.