ANN Model For SiGe HBTs Constructed From Time-Domain Large-Signal Measurements

We construct a large-signal artificial neural network (ANN) model for SiGe HBTs, directly from time-domain large-signal measurements. It is known that HBTs are very sensitive to self-heating and therefore we explicitly study the effect on the model accuracy of the incorporation of the self-heating effect in the behavioural model description. Finally, we show that this type of models can be accurate at extreme operating conditions, where classical compact models start to fail

SILICON-GERMANIUM HETEROJUNCTION BIPOLAR TRANSISTORS FOR LARGE-SCALE LOW-POWER CRYOGENIC SENSING SYSTEMS

Cryogenic low noise amplifiers (LNAs) are one of the key components in many emerging applications such as radio astronomy or quantum computing in which a weak incoming signal needs to be read out. There have been extensive studies on the feasibility of leveraging silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) to implement cryogenic LNAs in the past. The deployment of such LNAs in the future large-scale systems in radio astronomy or quantum computing is contingent upon the possibility of developing LNAs with reduced DC power dissipation to enable the cooling of a large number of array elements inside a cryogenic cooler. In this dissertation, we focus on the cryogenic operation of SiGe HBTs at reduced supply voltages for the implementation of ultra low- power LNAs and their applications for scalable receiver systems. In addition, the limitations of the SiGe HBT cryogenic models for the operation at high current densities are investigated for the implementation of modern high speed SiGe HBT circuits

A Method to Simultaneously Extract the Small-Signal Equivalent Circuit and Noise Parameters of Heterojunction Bipolar Transistors

A method to extract the elements of the small-signal equivalent circuit and the noise parameters (NPs) of heterojunction bipolar transistors (HBTs) is presented. The extraction is done by simultaneous fitting of the measured S-parameters, noise figure (for a well-matched impedance), and NPs (estimated using the so-called F50 method). An additional error term, given by the root square sum of the differences between the NPs estimated from the F50 method and the NPs directly computed using the Hawkins model, is considered in order to avoid nonphysical results in the extraction of the intrinsic noise sources. To obtain the initial values of the equivalent-circuit elements, analytical expressions are applied under a number of bias conditions, namely, reverse bias, forward bias, and active bias. Experimental verification of the extraction of the equivalent-circuit elements and NPs of an HBT, up to 8 GHz, are presented, and the NPs are compared to those measured with an independent (tuner-based) method. The behavior of Fmin, extracted using the proposed method, as a function of the HBT collector current, is also presented.Peer Reviewe

Device Characterization and Compact Modeling of the SiGe HBT in Extreme Temperature Environments

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\u27s 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\u27s 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\u27s 78 parameters. The device\u27s 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

Silicon Germanium BiCMOS Integrated Circuits for Scalable Cryogenic Sensing Applications

This dissertation is focused on an investigation of BiCMOS cryogenic low noise amplifiers (LNAs) based on Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for simultaneous low noise and low power design and also taking advantage of CMOS circuitry for adding flexibility to the LNA design. Cryogenic LNAs\u27 scalability challenges are discussed and addressed in the dissertation. To achieve that, first, HBTs of three state-of-the-art technologies are characterized and modeled at cryogenic temperature. It is shown that SiGe HBT provides a promising compromise of noise temperature, power consumption, and bandwidth. Moreover, a scalable on-chip approach is proposed and verified for biasing of SiGe HBTs based LNAs. Finally, the first cryogenic re-configurable LNA is designed, implemented, and measured