Enhanced Emitter Transit Time for Heterojunction Bipolar Transistors (HBT)

Simulation results are presented to study the performance of improved emitter transit time using AlGaAs-GaInP composite emitter heterojunction bipolar transistor (HBT). This composite emitter HBT shows significant reduction of emitter- base capacitance C BE and improved high frequency performance. In our simulation we use Medici (2-D simulator) as a simulator. The composite emitter HBT has been compared with the conventional HBT. Results show superior performance of the composite emitter design over conventional one in terms of reduced C BE . The C BE achieved with the composite emitter design was 55% lower compared to conventional designs. However, there are no variations with the collector current which provides enhanced frequency response for a composite emitter design.