Geometrical scaling and radiation effects in silicon-germanium heterojunction bipolar transistors

The silicon-germanium heterojunction bipolar transistor (SiGe HBT) is the first practical bandgap-engineered device to be realized in silicon. SiGe HBT technology combines transistor performance competitive with III-V technologies with the processing maturity, integration levels, yield, and hence, cost commonly associated with conventional Si fabrication. In 1997, SiGe HBT technology emerged from the research laboratory and entered manufacturing on 200-mm wafers and the commercial RF and microwave markets [1]. Recently peak f_T above 200 GHz [25], [31] and peak f_max close to 200 GHz [19], [31] have been achieved in SiGe HBT technology, which make the SiGe HBT a candidate for 40 Gb/s (or even higher speed) applications in optical communication systems.; This dissertation begins with a presentation of the fundamental physics in SiGe HBTs. The high frequency characterization of the transistors is addressed in Chapter 2, followed by a discussion of high frequency measurement procedures in Chapter 3.; In Chapter 4, width scaling, length scaling, and stripe number scaling are quantified from an RF design perspective at 2 GHz. The results show that a SiGe HBT with emitter area A_E = 0.5 × 20 x 6 μm 2 is optimum for low noise applications at J_C = 0.1 mA/μm 2 and f = 2 GHz using the design methodology which can realize both optimal noise matching and input impedance matching almost simultaneously with the simplest matching network.; The SiGe profile design tradeoffs for low noise RF applications at a given technology generation are discussed in Chapter 5. Newly designed SiGe profiles improve the minimum noise figure (NF_min) without sacrificing gain, linearity, frequency response, or the stability of the SiGe layer.; Chapters 6, 7, 8 and 9 discuss radiation effects in SiGe HBTs. A comparison of the effects of gamma irradiation on SiGe HBT and Gallium-Arsenide (GaAs) HBT technologies is investigated in Chapter 6, followed by a study of the effects of 63MeV proton irradiation on SiGe:C HBTs in Chapter 7. Chapter 8 presents the first investigation of low energy (1.75 MeV) proton irradiation in SiGe HBTs and proton energy effects in SiGe HBT technology, followed by the discussion of the effects of operating bias conditions on the proton tolerance of SiGe HBTs in Chapter 9.; Finally, Chapter 10 gives the conclusions of this investigation and suggestions for future work in this area.