Characteristics of an InP-InGaAs-InGaAsP HBT

The dc characteristics of an interesting heterojunction bipolar transistor with an InGaAs-InGaAsP composite-collector structure are studied and reported. Due to the insertion of an InGaAsP setback layer at the base-emitter heterojunction, the potential spikes as well as the electron blocking effect are suppressed significantly. In addition, the presence of an effective base-collector homojunction substantially reduces the current blocking effect. The studied device shows good dc performances including the small offset and saturation voltage without degrading the breakdown behavior. A typical dc current gain of 118 and the desired current amplification over 11 decades of the magnitude of collector current I/sub C/ are obtained.