CHARACTERIZATION AND COMPACT MODELING OF SILICON-GERMANIUM HETEROJUNCTION BIPOLAR TRANSISTORS FROM ROOM TO CRYOGENIC TEMPERATURES

Silicon-Germanium Heterojunction Bipolar Transistors (SiGe HBTs) are preferred for quantum computing (QC) readout circuits due to their high gain and speed as well as the integration with complementary metal-oxide-semiconductor (CMOS) technology. The device physics of SiGe HBTs at cryogenic temperatures (CT), like carrier scattering, carrier transport, high-injection effects were not systematically and physically investigated. Thus, a physical compact model for circuit simulation did not exist at the start of this thesis work. In this work, the measurement setup has been built for obtaining directcurrent (DC) and small-signal characteristics from medium to high frequencies over a wide temperature range. The radio frequency (RF) power of network analyzer and integration time of source monitor units have been investigated to ensure the accuracy of the DC and smallsignal measurement. The key electrical parameters of SiGe HBTs have been characterized. The temperature trend of the transfer current, base current, sheet resistance, depletion capacitance, and built-in voltage, zero-bias hole charge have been extensively demonstrated and physically analyzed. Based on the comprehensive investigation on the electrical parameters over a wide range of temperatures, the following work consists of two parts: (1) the existing analytical formulations for various electrical components have been compared for their validation, and (2) in case of evident discrepancies the physical origin has been analyzed and valid compact formulations have been derived.