The performance potential of p-n-p heterojunction bipolar transistors

The performance of P-n-p AlGaAs/GaAs heterojunction microwave and switching transistors is compared to that of N-p-n structures. The maximum frequency of oscillation calculated for an optimized P-n-p microwave transistor is found to be only 29 percent less than that for an optimized N-p-n device. Similarly, the switching time of a P-n-p in a digital circuit is found to be only 28 percent greater than that of an N-p-n. These results are explained in terms of the parameters of a compact transistor model. The potential for use of the P-n-p HBT in microwave and switching applications is discussed in light of both performance and fabrication details.