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Fabrication of site-controlled quantum structures for optoelectronic devices

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Title: Fabrication of site-controlled quantum structures for optoelectronic devices
Author(s): Cheng, Chien-Chia
Director of Research: Cheng, Keh-Yung
Doctoral Committee Chair(s): Cheng, Keh-Yung
Doctoral Committee Member(s): Hsieh, Kuang-Chien; Feng, Milton; Jin, Jianming
Department / Program: Electrical & Computer Eng
Discipline: Electrical & Computer Engr
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Molecular beam epitaxy Site-controlled Quantum dots Nanoimprint lithography Quantum Structure Lattice Optoelectronics
Abstract: Over the past two decades, there has been great interest in integrating semiconductor quantum dots (QDs) into electronic and optoelectronic devices, utilizing the three-dimensional quantum confinement effect to improve device performance as well as to create devices with new functionalities. However, despite its prevalence in fabrication of QDs, self-assembled QD growth via the Stranski–Krastanov growth mode does not provide much control over QD size, spatial position, and uniformity, and thus can only be used in limited applications. Contrarily, site-controlled QD (SCQD) fabrication has been considered a promising alternative for its abilities to improve QD homogeneity and precisely address the positions of QDs. In this study, two pathways to fabricate SCQDs are developed and explored by utilizing soft photocurable nanoimprint lithography (soft NIL) to create nanoscale patterns. The first is a bottom-up method which leads to the formation of “regrown QDs”. In this approach, high optical quality InAs QDs are regrown in designed nucleation sites over GaAs substrate, and the effects of process and growth parameters on the structural and optical properties of regrown QDs will be examined. In contrast, “pillar QDs” are fabricated from quantum wells (QWs) by the top-down approach, in which strained InGaAs single QW patterned by soft NIL is etched into pillar QB array. Extremely narrow photoluminescence linewidth from a pillar QB array suggests an unexplored phenomenon due to interaction between periodically-arranged optical emitters. A new model, quantum structure lattice, to explain the experimental results will be proposed and discussed.
Issue Date: 2012-06-27
Rights Information: Copyright 2012 Chien-Chia Cheng
Date Available in IDEALS: 2012-06-27
Date Deposited: 2012-05

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