Award Date

5-1-2025

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Electrical and Computer Engineering

First Committee Member

R. Jacob Baker

Second Committee Member

Sarah Harris

Third Committee Member

Brendan Morris

Fourth Committee Member

Alexander Barzilov

Number of Pages

213

Abstract

Single-photon avalanche diodes (SPADs) are solid-state devices capable of providing large current pulses in the milliampere range in response to incident photons. The large gain inherent to SPADs makes them a popular technology for photon-counting applications, but their operation can be hindered by long recharge times, which necessitates the use of active quenching to reduce dead times and increase detection rates. For the prompt gamma/neutron radiation experiments conducted at the Nevada National Security Site, photomultiplier tubes (PMTs) have been the primary photodetector of choice, but their continued use is expected to dwindle as it becomes increasingly difficult to source quality PMTs due to aging of the technology. As a result, alternative means of photodetection are currently being researched, with SPADs being one of the devices of interest.This thesis details the development of high dynamic range, actively quenched silicon-germanium (SiGe) SPADs capable of meeting the performance targets set by the NNSS for the intended application, which requires reset times of 1-2ns maximum and full-width-half-max output pulses in the 100-500ps range or less. The beginning of this process involved testing a multitude of SiGe SPADs previously developed by the lab using the Austriamicrosystems 0.35μm SiGe BiCMOS process and determining which device structure and size yielded the shortest pulse widths (an indicator of a small junction capacitance, a desired parameter for the aforementioned metrics). Once the ideal SPAD structure was identified, a 5μm-by-5μm square structure without guard rings, the device was further tested to characterize its current response to varying degrees of reverse biasing. Using this information, an LTspice model was developed to emulate the SPAD’s behavior to facilitate more accurate simulations of the final two active quenching integrated circuit designs, which were developed using TSMC’s 180nm process. The variable-load active quenching design was able to achieve a nominal reset time of 738ps with a 103ps FWHM output while the latching active quenching design provided a nominal reset time of 735ps with a 73ps FWHM output, indicating that both designs can theoretically resolve 1Gcps (gigacounts per second) reliably. Preliminary layouts of the actively quenched SPAD pixels with integrated analog counting were created using TowerJazz’s 180nm SiGe BiCMOS process, the process in which the final chip will ultimately be manufactured.

Keywords

application-specific integrated circuit; array; current mode; detector; pixel; time-gated

Disciplines

Electrical and Computer Engineering | Engineering | Physics

File Format

pdf

File Size

18400 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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