SIMULATION AND DESIGN OF INALAS INGAAS PNP HETEROJUNCTION BIPOLAR-TRANSISTORS/

The performance capabilities of InP-based pnp heterojunction bipolar t ransistors (HBT's) have been investigated using a drift-diffusion tran sport model based on a commercial numerical simulator. The low hole mo bility in the base is found to limit the current gain and the base tra nsit time, which limits the device's cutoff frequency. The high electr on majority carrier mobility in the n(+) InGaAs base allows a reductio n in the base doping and width while maintaining an adequately low bas e resistance. As a result, high current gain (>300) and power gain (>4 0 dB) are found to be possible at microwave frequencies, A cutoff freq uency as high as 23 GHz and a maximum frequency of oscillation as high as 34 GHz are found to be possible without base grading. Comparison i s made with the available, reported experimental results and good agre ement is found. The analysis indicates that high-performance pnp InP-b ased HBT's are feasible, but that optimization of the transistor's mul tilayer structure is different than for the npn device.