The influence of bandgap narrowing and impurity deionization on the characteristics of silicon bipolar microwave transistors

The emitter regions of Silicon bipolar microwave transistors are usually heavily doped. The magnitude and distribution of impurity concentrations of the emitter and base regions depend upon the designs and technologies of the transistors. Both the bandgap narrowing and the impurity deionization have influence on majority carrier concentrations, minority carrier concentrations and the characteristics of transistors. Considering only one of them may lead to somewhat unsatisfactory results. In this paper an analytical treatment of ideal emitter injection-efficiency-limited current gain of a bipolar device is presented that includes the effects of bandgap narrowing, impurity deionization and Fermi-Dirac statistics. The results predicted by the present analysis are compared with those from other sources, and we can hereby draw some useful conclusions.