Development of silicon germanium-based power heterojunction bipolar transistors and their application to microwave power amplification.

摘要

The dissertation research is focused on the development of high power and high efficiency SiGe/Si HBTs that can be operated at high microwave frequencies and the demonstration of high frequency MMIC power amplifiers using SiGe/Si power HBTs. The design, fabrication and performance characteristics of X-band (8.4 GHz) and Ku-band (12.6 GHz) power SiGe/Si HBTs have been investigated. State-of-the-art power output has been obtained from X-band SiGe/Si HBTs. With 25% PAE, 20-emitter finger HBTs are able to provide 28.45 dBm (700 mW) of output power. A peak PAE of 42.1% was measured from 10-emitter finger common-base HBTs and a power density of 0.96 mW/μm 2 was measured from 4-emitter finger CE HBTs. The first Ku-band high power SiGe/Si HBT has been successfully developed with advanced process techniques and optimized heterostructure and layout design. An f_max of 100 GHz was achieved from 9-emitter finger common-base HBTs with emitter area of 403 μm2. An output power of 22.3 dBm at the peak PAE of 21.5% was measured with an associated power gain of 7 dB. The P_−1dB is about 23 dBm (200 mW) and the maximum P_out was measured to be 24.4 dBm. The highest peak PAE of 22.8% was measured with associated power gain of 7.4 dB.; The design and fabrication of SiGe/Si HBT-based X-band (8.4 GHz) MMIC power amplifier has been studied. Large-signal modeling of SiGe/Si power HBTs, using the conventional Gummel-Poon model and equivalent circuit modeling of the spiral inductors and MIM capacitors, were investigated for the implementation of the power amplifier circuit. Reasonably good accuracy has been achieved with this modeling process. The interplay between the Kirk effect and the Early effect at high bias levels has been analyzed. The MMIC power amplifier exhibits an output power of 23 dBm at the peak PAE of 12%, and a saturation output power of 25 dBm. A peak PAE of 16% can be measured from this circuit.; A detailed study of forward-bias electrical-thermal stress induced degradation of Si_1−xGe_x/Si HBTs was conducted. It was found that the observed gradual degradation is mainly caused by recombination enhanced impurity diffusion (REID) of the boron atoms from the base layer into the adjacent emitter and collector layers. An analytical REID model was formulated, for the first time, based on low-level injection theory. Good agreement of the gradual degradation behavior is obtained with calculated results based on this model, which takes into account base dopant outdiffusion and the associated formation of parasitic energy barriers near the heterojunction.