Unequally Valued Emitter Ballasting Resistors Optimum Design of Multi-finger Power GeSi HBTs

Multi-finger structure is commonly used in microwave power GeSi HBTs (heterojunction bipolar transistors). Usually equally valued emitter ballasting resistors are added to improve thermal stability of the devices. However, self-heating and thermal coupling effects make the temperature distribution on emitter fingers non-uniform, so the equally valued ballasting resistors structure is not optimum. In this paper, an unequally valued ballasting resistors structure is presented, which could improve the uniformity of devices' temperature distribution effectively, and decrease the highest temperature to a certain extent.