Staffan Bruce

PhD Thesis, Uppsala University, Acta Universitatis Upsaliensis 479,
ISBN 91-554-4558-6, November 1999.

Introduction (126 pages)
in Postscript, 19.2M ; compressed (gz), 1932K
Papers included in the thesis (58 pages)
in Postscript, 8.2M ; compressed (gz), 2283K

Paper copies of the thesis can be obtained from Ylva Johansson, Signals and Systems Group, Uppsala University, Box 534, SE-75121 Uppsala, Sweden.

Outline:

With the progress in Silicom Germanium technology, fabrication of high performance heterojunction bipolar transistors has become fesible and devices with f_max of 90 GHz in a common-emitter configuration have been achieved with repeatability. This opens the possibility of designing circuits operating in the millimeter-wave frequency region using such transistors. This thesis deals with different aspects of the device.

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 trans-impedance 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 noise corner frequency are discussed.

Keywords:

Silicon Germanium, SiGe, Heterojunction Bipolar Transistor, HBT, Large-signal modeling, thermal time constant, low-frequency noise, coherence, trans-impedance amplifier.

Related publications:

Extraction of thermal time constant in HBTs using small signal measurements.Electronics Letters 1997.
In Postscript : compressed(gz) 64K , uncompressed 334K.

On the design of a 55 GHz Si/SiGe HBT frequency doubler operating close to fmax. Proc. 26th European Microwave Conference, Prague 1996.
In Postscript : compressed(gz)584K , uncompressed1.56M.

Development, implementation and verification of a physics-based Si/SiGe HBT model for millimeter-wave non-linear circuit simulations. Proc. 26th European Microwave Conference, Prague 1996.
In Postscript : compressed(gz)30K , uncompressed131K.