Analysis of improved DC and AC performances of an InGaP/GaAs heterojunction bipolar transistor with a graded Al/sub x/Ga/sub 1-x/As layer at emitter/base heterojunction

An InGaP/GaAs heterojunction bipolar transistor (HBT) with a continuous conduction-band structure is demonstrate and theoretically investigated. This device exhibited good performance, including lower turn-on voltage, lower offset voltage, and smaller collector current saturation voltage. The novel aspect of device structure design is the adoption of the compositionally linear-graded AlGaAs layer between the InGaP-emitter and GaAs-base layers. Therefore, the studied device shows better DC and AC performances than a conventional device. Consequently, this provides a substantial benefit for practical analog and digital applications, especially, for lower operation voltage, lower power consumption, commercial and military products.