Characteristics of InGaP/GaAs delta-doped heterojunction bipolar transistor

An InGaP/GaAs heterojunction bipolar transistor with a δ-doped sheet structure has been fabricated successfully. High current gain, especially in the very low collector current regime, low collector-emitter offset voltage (ΔVCE) characteristics are obtained. There is an extremely small offset voltage of about 55 meV due to the elimination of the potential spike at the emitter-base heterojunction by a δ-doped sheet and a 50 A very thin setback layer. On the other hand, the high current gain of 280 also reveals that the degradation of current gain due to the potential spike can be avoided. In addition, the influence of the δ-doped sheet and the undoped setback on device properties is studied.