Base design for Pnp InAlAs-InGaAs heterojunction bipolar transistors

The design of the n+ base region for Pnp InAIAs-lnGaAs heterojunction bipolar transistors has been studied using a two dimensional, numerical approach based on a commercial simulator. The hole's low minority carrier mobility and diffusion length in the base limit the device's performance. However, the electron's high mobility In InGaAs allows for a thinner base region while maintaining a low base series resistance which Improves the device's gain and cutoff frequency. As a result, high current gain (> 200) and power gain (> 30 dB) are found to be possible at microwave frequencies. In this work, the effects of base doping and thickness on the device's high frequency performance are investigated for device optimization. Peak values of f(T) (17 GHz) and f(T) (30 GHz) are found to be possible. The results also suggest that further enhancements in device performance can be achieved using compositional grading of the base region.