SIGE-HBTS WITH HIGH F(T) AT MODERATE CURRENT DENSITIES

Silicon-germanium heterojunction bipolar transistors (SiG-HBTs) have b een developed with regard to high cutoff frequencies within a wide col lector current range. Unity current gain frequencies f(T) high as 116G Hz were obtained at a collector current density of 2 x 10(5) A/cm2. In addition, the FWHM of cutoff frequency f(T) against collector current exceeds one and a half decades. Calculations indicate that the ratio of the collector to emitter area essentially determines the current de nsity range of a high frequency HBT.