DC CHARACTERIZATION OF HBTS USING THE OBSERVED KINK EFFECT ON THE BASE CURRENT

Large parasitic series resistances of the heterostructure bipolar tran sistors are shown to cause a sharp rise in the base current of the Gum mel plot at high current levels. This effect is analysed and attribute d to a forward-biased base-collector junction due to the large voltage drop across the collector series resistance of the device. The occurr ence or this effect results in a severe reduction in current gain of t he device at high current levels. A DC Ebers-Moll model is presented w ith ail the parameters extracted from DC characterisation of the HBT, and an excellent fit between the model and experimental data is obtain ed. The method can be used to determine the base, collector and emitte r series resistances of the bipolar transistors for DC applications. F inally. the effect of temperature on the onset of this effect is demon strated. (C) 1998 Elsevier Science Ltd. All rights reserved.