功率晶体管的发射极设计

本文讨论功率晶体管设计中设计发射极时所需考虑的两个问题。一个是在给定的注入条件下如何保证足够大的电流放大;另一个是如何提高发射极发射电流的有效面积。文中着重分析在各种注入条件下发射结面上发射极电流密度的分布,亦即所谓基区电阻自偏压截止效应,最后给出主要结论。

THE DESIGN OF POWER TRANSISTOR EMITTER

In the design of an emitter of power transistors, the main problem is to attain good current amplification factor β for a given injection level. At a higher injection level, the current amplification factor drops off as the emitter current density is increased. One of the commonly used methods to reduce this fall-off is by increasing the emitter area. On account of the socalled "base region self-crowding effect", this would make the emitter current density not uniform over the emitter junction area, the current density dropping off rapidly at regions far from the base contact. In this paper, this effect is analyzed quantitatively for nearly all injection levels both for circular and comb structures of the junction. An "exponential decay" for the emitter current density distribution, and an effective emitter area are obtained. These results may give some reference for the design of power transistors.