Novel silicon-germanium BiCMOS device physics phenomena and their application to power amplifiers

The high-speed performance of SiGe heterojunction bipolar transistors (HBTs) and MOSFETs due to aggressive scaling has made SiGe BiCMOS technology a strong contender for RF/microwave applications. While low-power high-speed circuits have been successfully implemented on SiGe BiCMOS platform, high-power and high-frequency power amplifiers using SiGe HBTs or CMOS have remained to be the most challenging circuit module in a wireless system due to unresolved critical issues. This thesis describes several novel device physics phenomena regarding the implementation and optimization of high-power SiGe HBTs and RF power MOSFETs in SiGe BiCMOS technology as well as their application in microwave power amplifiers. Through power gain analysis, the fundamental difference between the common-emitter (CE) and the common-base (CB) configurations in bipolar transistors is revealed for RF power applications. The role of Ge profile on power gain performance of SiGe power HBTs with constant Ge strain and the impact of emitter ballast and base ballast resistors on the RF performance of SiGe power HBTs are also clarified by analytical derivation, simulation and experiment. The study of proton radiation effects on large-signal power performance of high-power SiGe HBTs reveals the potential of these power devices for space applications. In addition, the substrate parasitic effects on the power gain characteristics of RF MOSFETs for both common-source (CS) and common-gate (CG) configurations and the proton radiation tolerance of multi-finger RF power MOSFETs are investigated. Based the device physics study, a 24GHz SiGe MMIC power amplifier was designed with detailed description on unit device selection, operation configuration, circuit topology, ballast resistor design and interconnect parasitic modeling. As a result, high output-power, high power-gain and high power-added efficiency (FAE) are achieved with a compact chip size.