Self-Heating Characterization of SiGe:C HBTs by Extracting Thermal Impedances

In this letter, the self-heating effects in SiGe heterojunction bipolar transistors (HBTs) and the influence of the emitter widthWEand the emitter lengthLEon all of the thermal parameters are presented for the first time by extracting the thermal resistanceRTH, capacitanceCTH, and time constantTTH. First, we discuss the thermal impedance extraction method. The approach is based on both dc and ac measurements within the 30 kHz–6 GHz low-frequency range. Then, the self-heating influences of various SiGe HBT topologies are presented. Finally,RTH,CTH, andTTH, which were extracted from different transistor geometries, are compared.