Numerical modeling and design of Pnp InAlAs-InGaAs heterojunction bipolar transistors

Pnp InAlAs/InGaAs heterojunction bipolar transistors have been studied using a two dimensional, numerical approach based on a commercial simulator. Initial simulation results have shown good agreement with the available experimental data. This paper examines the effects of the epitaxial layer parameters and optimization of the transistor´s multi-layer epitaxial structure. Due to the small hole diffusion length, base widths approaching 30 nm are needed to achieve significant current gain (>100) and large f_τ (>10 GHz). The high majority carrier electron mobility in the base allows the base resistance to remain small as the base width and doping are reduced so that an f_τ greater than 20 GHz and an f_max greater than 30 GHz are possible