Physics, Compact Modeling and TCAD of SiGe HBT for Wide Temperature Range Operation

One of the remarkable characteristics of SiGe HBT is the ability to operate over a wide tem-perature range, from as low as sub 1K, to as high as over 400 K. The SiGe HBT investigated and measured in this work is a first-generation, 0.5 mm SiGe HBT with fT = fmax of 50 GHz/65 GHz and BVCEO=BVCBO of 3.3 V/10.5 V at 300 K. The base doping is below but close to the Mott-transition (about 31018 cm3 for boron in silicon). In this dissertation, some important SiGe HBTs physics at cryogenic temperature are analyzed. New compact models equations for SiGe HBT are devel-oped, which can function from 43 to 393K. Device TCAD simulations are used to help understand the device physics at cryogenic temperatures. First, the temperature dependence of semiconductors critical metrics are reviewed, including bandgap energy Eg, effective conduction band density-of-states NC and valence band density-of-states NV, intrinsic carrier concentration at low doping ni, bandgap narrowing DEg, carrier mobility m, carrier saturation velocity nsat and carrier freezeout. The dc and ac low temperature performance of SiGe HBT are analyzed, including collector current density, current gain, Early effect, avalanche multiplication factor, transit time, cut-off frequency and maximum oscillatio