An Evaluation of Extraction Methods for the Emitter Resistance for InP DHBTs

The emitter series resistance is a very important parameter for bipolar transistors since it can have a significant impact on both the DC and high-frequency characteristics of transistors. Its accurate determination is quite difficult due to the complicated emitter material stack and the lack of suitable test structures. Thus, extraction methods that rely on transistor terminal characteristics must be used instead. In this paper, the accuracy of several widely used extraction methods for the emitter resistance has been investigated for three different type I InP DHBT technologies by applying the methods to both measured and simulated data. Since for the latter the emitter resistance is exactly known, it allows a reliable evaluation of the accuracy and the applicability of a method.