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Title:Modeling of devices for gallium-nitride-based integrated photonics
Author(s):Su, Guan-Lin
Director of Research:Dallesasse, John M.
Doctoral Committee Chair(s):Dallesasse, John M.
Doctoral Committee Member(s):Chew, Weng Cho; Feng, Milton; Jin, Jianming
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):III-Nitrides (III-Ns)
Self-assembled quantum dots (SAQDs)
Integrated photonics
Abstract:Credited as "the most important semiconductor since silicon (Si)," gallium nitride (GaN) has received a tremendous amount of attention during the past two decades due to its superb material properties. While the wide band gap and high electron saturation velocity make it especially suitable for high-power and high-frequency microelectronics, the ultra-wide spectral coverage by the direct band gaps of aluminum gallium nitride (AlGaN) and indium gallium nitride (InGaN) gives nitride semiconductors a central stage in optoelectronic devices. Various applications such as medical inspection, sterilization, optical storage, solid-state lighting, and the blue-green light sources in full-color displays have made GaN-related devices influential in people’s daily life. Most of the research to date on III-nitride (III-N) semiconductors has concentrated on the growth of novel nano-structures, the epitaxy of high-quality materials, and the fabrication of devices targeting unprecedented performance. Work on the underlying physics, device diagnosis, or even the proposal and design of devices with new functionalities has been relatively scarce. Even though the theory of III-N quantum wells (QWs) is fairly mature, QW structures face overwhelming strain that limits the maximum indium incorporation and generates a high density of threading dislocations. These issues lead to difficulties in extending the emission wavelength to the "green-yellow gap," low device efficiencies and short lifetimes. These undesirable features have been motivating the pursuit of novel III-N active materials, but in fact understanding the fundamental physics beneath these nano-structures plays an equally important role, as it serves as an evaluating or even predicting process for designing new optoelectronic devices. While a great amount of research energy has been focused on exploring GaN’s the effectiveness for photon-generating processes, its capability in photon-manipulating processes has been significantly overlooked. The asymmetric wurtzite lattice actually implies strong optical effects, which, combining with the piezoelectric effect, make voltage-controlled optically-responsive devices possible. Furthermore, taking advantage of the establishing GaN-on-Si technology, such devices can be integrated with high-speed, high-power GaN transistor driving circuitries or even be transferred to other material platforms with a minimal amount of cost. These unique properties not only make GaN a promising material for optical signal processing but also open up an emerging field of "GaN integrated photonics." The first part of this work focuses on the theoretical study of InGaN/GaNself-assembled quantum dot (SAQD) gain materials and corresponding lasers emitting at visible wavelengths. Following a discussion of adopting III-Ns as an active material in the telecommunications wavelengths, the second part of the thesis considers the design of novel voltage-controlled photonic components, such as polarization rotators (PRs) and gratings, for realizing stable polarization-division multiplexing in coherent optical communication systems. The last part of the thesis introduces experimental work on the development of InP-based laser gain chips, which are the most efficient light source in the optical telecommunications window and will be interfaced with the GaN-based photonic elements. It is expected that the model of the InGaN/GaN SAQDs can be extended to study other nano-structures, and the model of voltage-controlled PRs and gratings can contribute to conceptualization and realization of GaN integrated photonics.
Issue Date:2016-07-11
Rights Information:Copyright 2016 Guan-Lin Su
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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