Cubic phase gallium nitride photonics integrated on silicon(100) for next-generation solid state lighting

Liu, Richard Dicky

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https://hdl.handle.net/2142/108450 Copy

Description

Title

Cubic phase gallium nitride photonics integrated on silicon(100) for next-generation solid state lighting

Author(s)

Liu, Richard Dicky

Issue Date

2020-07-09

Director of Research (if dissertation) or Advisor (if thesis)

Bayram, Can

Doctoral Committee Chair(s)

Bayram, Can

Committee Member(s)

• Goddard, Lynford
• Dallesasse, John
• Lee, Minjoo L
• Yu, Anthony W

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

cubic gallium nitride, photonics, polarization-free, LED, silicon

Abstract

Semiconductors made of gallium nitride (GaN) and its compounds (AlInGaN) have transformed the visible light emitting diode (LED) industry thanks to their direct bandgap across the entire visible and ultraviolet spectra. Despite its success, the conventional hexagonal-phase GaN has fundamental disadvantages in performance and cost that hinder market adoption. These include: internal polarization field ( MV/cm2), high acceptor activation energy (260 meV), low hole mobility (20 cm2/V), and expensive substrates (Al2O3, SiC). Gallium nitride also crystallizes in the cubic crystal that has a higher degree of symmetry. This leads to some advantageous properties for light emitting applications: polarization-free, lower acceptor energy (200 meV), and higher hole mobility (150 cm2/V). These advantages are critical for the development of the next-generation solid state lighting. Difficulty in its synthesis stemming from the large crystal lattice mismatch, chemical incompatibility, and phase metastability has prohibited the growth of high quality semiconductor crystals that are device-worthy. This thesis explores a method of synthesizing phase-pure, high-quality cubic GaN crystals on nanopatterned Si(100) substrates via hexagonal-to-cubic phase transition, and the thesis presents a comprehensive material characterization of the crystals. Crystal growth geometry modeling of GaN on nanopatterned Si(100) substrates is used to estimate the necessary patterning parameters to facilitate complete phase transition. The cubic GaN material is then studied using structural characterization techniques including scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. The carrier recombination properties are studied using photoluminescence, Raman spectroscopy, and cathodoluminescence. The cubic GaN synthesized using the phase transition method on carefully patterned Si(100) substrates is shown to be phase-pure, defect-free, and optically superior. Material properties such as internal quantum efficiency, Varshni coefficients, and defect levels are extracted from the experiments. Other work on hexagonal GaN light emitters on silicon substrates, chamber conditioning for metalorganic chemical vapor deposition of III-nitrides, and space-based laser instruments for NASA missions is also discussed. Class lab module development and outreach activities are included.

Graduation Semester

2020-08

Type of Resource

Thesis

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http://hdl.handle.net/2142/108450

Copyright and License Information

Copyright 2020 Richard Dicky Liu

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