Effect of interfacial oxide on static and high-frequency performance in poly-emitter bipolar transistors under high-level injection

We report on a theoretical investigation of the effect of interfacial oxide on both static and dynamic performance in polycrystalline silicon emitter bipolar transistors. The calculation is carried out up to 0.9 V, before the onset of the Kirk effect. From the model, it is found that the current gain increases and the forward transit time decreases as interfacial oxide thickness increases. Furthermore, both the current gain and the forward transit time decrease as recombination velocity increases. In addition, the intrinsic base resistance remains almost constant as interfacial oxide thickness increases, and increases as recombination velocity increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of bipolar transistors operating under high-level injection.