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Title:Scalable designs and methods for heterogeneous electronic-photonic integrated circuitry
Author(s):Carlson, John Anthony
Advisor(s):Dallesasse, John M
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):photonic integration
III-V on silicon
gallium nitride
CMOS compatiblilty
scalable processes
Abstract:A set of semiconductor designs shown to be capable of facilitating scalable and reconfigurable layouts for electronic-photonic integrated circuitry is presented. Three emphases are established to outline and discuss the methods and advantages of merging stand-alone optical components into integrated heterogeneous systems, specifically for implementing optical sensing, efficient laser wavelength tuning, and III-V-on-Si semiconductor fabrication techniques together on a single platform. Considerations regarding the optical geometries and power efficiency of each design are reiterated to assure that each design is compatible with the goals of system-level integration in either biochemical point-of-use or telecommunications applications. These three approaches to scalable photonic designs are then investigated in their ability to offer dynamic controls of optical signals and their novel usage of heterogeneous material patterning. The optical sensing platform directly integrates multiple linear variable filters (LVFs) atop a CMOS image sensor for electronic controls of detecting a biochemical fluorescent or absorptive optical signal signature, enabling good wavelength resolution (3.77−6.08 nm) over a wide-band detection spectrum. Detection limits of 0.28 nM for Quantum Dot emitters and 32 ng/mL for near-infrared fluorescent dyes are found in this integrated design, providing comparable results in the compact optical platform to conventional laboratory spectrometers. The instrument is then extended in its usage by testing on point-of-use detection tests via discerning the concentration of free-chlorine in water colorimetrically. The tunable laser cavity design integrates together a GaN waveguide into a standard InGaAsP telecom (1550 nm) edge-emitting laser atop silicon, allowing for wide-band tuning via the strong anisotropic effects solved for in wurtzite GaN. A tuning parameter based off a refractive index variation, Δ𝑛, is found to be at |1.75∙10E−4|, based off the electro-optic effects in conjunction with an etched grating geometry designed directly into the coupled GaN waveguide, with the structure further extended into a Y-branch laser cavity to enable the Vernier effect for wideband tuning via mode-hopping. A separate GaN-based design, consisting of an RF signal modulator that launches a surface acoustic wave (SAW) into a cavity to produce a highly controllable refractive index variation, Δ𝑛, via the photo-elastic and photo-elastic effects, is found to produce a large tuning parameter of |1.84∙10E−3|. These effects are then described in their application to dynamically controllable effects for dense wavelength division multiplexing (DWDM) and how the underlying electronic platform enables this, providing advantages over larger footprint or less efficient designs. The fabrication techniques designed provide a method to enable bonding of III-V epitaxial wafers onto a silicon carrier wafer for large-scale processing before final bonding onto CMOS. A processing recipe takes bulk GaAs epitaxial structures and constructs a method for reversibly bonding and processing them on a silicon carrier wafer as III-V islands, ready for final large scale flip-chip bonding onto aligning CMOS features. Additional findings discuss the merits of various etch processes and techniques such that they are compatible to the heterogeneous III-V-on-Si patterning as laid out. The methods optimized allow for simultaneous, heterogeneous development of system-level device integration such that further processing can place various III-V devices side-by-side and process geometries in unison. Processing steps and their results are presented. The extension of this method to different III-V alloys beyond GaAs entirely is therefore considered for even larger-scale system design across photonic elements. Each set of findings presents both the relevant photonic device characteristics and also a method on how to intersect these devices with a paired CMOS electronic system on silicon, so that a single unified electronic-photonic schematic can be made. Accompanying these conclusions is a range of experimental work ranging from simulation studies, to full-scale integrable sensing designs and their testing, to detailed cleanroom-based fabrication processes for designing the system of III-V-on-Si patterns. A final set of conclusions relates the three tracks of research as being part of a common path forward in scalable photonics designs. Forecasts are then made on how the field of electronic-photonic integration and its applications utilized herein may yet evolve and potentially encompass findings or methodologies from this work.
Issue Date:2017-04-27
Rights Information:Copyright 2017 John Carlson
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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