Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level



Electrical Engineering


Simon S. Ang

Committee Member

G. Wayne Dietrich

Second Committee Member

H. Alan Mantooth

Third Committee Member

Jerry R. Yeargan


Applied sciences, Compact modeling, Extreme temperatures, Heterojunction bipolar transistors, Semiconductor device modeling, Silicon germanium


The silicon germanium heterojunction bipolar transistor, SiGe HBT, has very high frequency response but limited voltage range. Commercial communication applications in wireless and system integration have driven the development of the SiGe HBT. However, the device's excellent electrical performance goes beyond the commercial environment. The SiGe HBT performs exceptionally at low temperatures. The device DC current gain and AC small-signal gain significantly increase in the cryogenic temperature range. Applications at low temperatures with expansive temperature range specifications need an HBT compact model to accurately represent the device's performance.

In this work, a compact model referenced at 300K was developed to accurately represent both DC and AC electrical performance of the SiGe HBT over an extended temperature range, down to 93K. This single expansive temperature, SET, model supports all functions of circuit simulation; DC quiescent operation and AC frequency response. The SET model was developed from the Mextram 504.7 bipolar model and accurately represents full transistor operation over an extreme temperature environment. The model correctly simulates SiGe HBT DC output performance from saturation, through quasi-saturation and the linear region including impact ionization effects. This model was developed through a combination of physical calculations based on doping profiles and optimization techniques for modeling fitting. The SET model of this dissertation added 32 parameters to the original Mextram 504.7 model's 78 parameters. The device's static and dynamic performance over the full temperature range down to 93K was fitted with a single group of SET model parameters. The model results show excellent correlation with measured data over the entire temperature range.