Silicon Germanium heterojunction bipolar transistors : Large-signal modeling and low-frequency noise characterization aspects

Abstract: In this thesis, aspects of the Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) are addressed. A physics-based electrical large-signal model including thermal dependence has been developed and is implemented using a commercially available simulator package. Good agreement-is found between calculated data using the model and measured data. Equations for the electrical parameters based on physical data and a fitting procedure for finding parameter values concerning parasitic effects are presented. In addition, a technique for extracting very short thermal time constants using small signal measurements is presented. Using the large-signal model, a frequency multiplier employing a single SiGe HBT as the non-linear device has been designed and fabricated. The doubler operates with an output frequency of 55 GHz and performance can be well explained using the model. Low-frequency noise in the SiGe HBT has been studied, primarily using transimpedance amplifiers. Problems related to the measurement of low-frequency noise are discussed. The dominant noise source in a SiGe HBT is discriminated using direct two-channel noise measurements for a sweep of base resistance terminations of the device. By employing a device temperature variation the temperature dependence of the dominant source is further studied. A method for improved coherence measurements during a sweep of base resistance terminations is presented. A method for modeling low-frequency noise in a SPICE based simulator and aspects of the noisecorner frequency are discussed.