Effects of base and emitter doping gradients on the electrical performance of heterojunction bipolar transistors

The analytical equations of heterojunction bipolar transistors with nonuniform doping in the base and emitter has been developed. The comparison of the device characteristics between nonuniform and uniform doped HBTs show that the nonuniform doped HBT has higher current gain, higher cutoff frequency, lower base transit time, and lower emitter-base junction capacitance.