GROWTH OF InGaN MATERIAL AND DEVICE STRUCTURES IN A HIGH PRESSURE MOCVD REACTOR

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Conway, M. (2019). GROWTH OF InGaN MATERIAL AND DEVICE STRUCTURES IN A HIGH PRESSURE MOCVD REACTOR. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

This is an initial investigation of the super-atmospheric (1.5 – 2.5 bar(a)) Metal-Organic Chemical Vapor Deposition (MOCVD) growth of InGaN materials and experimental, device-like structures. The work was accomplished in a custom MOCVD reactor, specifically designed to produce laminar flow, at super-atmospheric pressures. Four main thrusts are included in this work; initial investigations into total group III flux and V:III ratio, barrier layer growth, and the effect of two growth conditions on photoluminescence, growth temperature and growth pressure/NH3 partial pressure.Practical limits on the Group-III flux were established. It was discovered that the group-III flux was a very important criteria, in the growth process. A rate that was too high, would cause group-III metals, especially indium, to be deposited on the surface of the substrate, but not incorporated into the crystal lattice. It was found that higher temperatures were required to produce photoluminescent materials in this high-pressure reactor, than in comparable low-pressure growths. The reasons for this are not well understood.The samples were all grown on sapphire substrates with a previously grown HVPE GaN layer on top. Preliminary work was performed on the buffer/nucleation layer. The current buffer/nucleation layer is still not completely epitaxial, and this is thought to be a major limiting factor on the current quality of the material and device-like structures in this work. However, this work significantly improved the buffer/nucleation layer, from its initial state, and has identified several important factors for improving the quality of the buffer layer and ultimately, opto-electronic devices.Also, photoluminescence over growth pressure and NH3 partial pressure was investigated. The samples in this thrust were grown from 1.5 bar(a) to 2.5 bar(a) or 0.55 to 0.91 bar(a) NH3 partial pressure. The results indicate that the photoluminescent efficiency of the samples increased, as their growth pressure increased.This work concludes with a preliminary recipe for photoluminescent InGaN, at super-atmospheric pressures and initial data, relating photoluminescence to specific process variables. The current growth recipe is given at the conclusion of this work. This recipe is not yet commercial quality; its photoluminescent intensity is not high enough (low IQE), and the growth mode, in the produced samples, is not epitaxial enough. The two issues are thought to be highly related.

Details
Author

Conway, Matthew

Title

GROWTH OF InGaN MATERIAL AND DEVICE STRUCTURES IN A HIGH PRESSURE MOCVD REACTOR

Physical Description

1 online resource (105 pages) : PDF

Date

2019

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

This is an initial investigation of the super-atmospheric (1.5 – 2.5 bar(a)) Metal-Organic Chemical Vapor Deposition (MOCVD) growth of InGaN materials and experimental, device-like structures. The work was accomplished in a custom MOCVD reactor, specifically designed to produce laminar flow, at super-atmospheric pressures. Four main thrusts are included in this work; initial investigations into total group III flux and V:III ratio, barrier layer growth, and the effect of two growth conditions on photoluminescence, growth temperature and growth pressure/NH3 partial pressure.Practical limits on the Group-III flux were established. It was discovered that the group-III flux was a very important criteria, in the growth process. A rate that was too high, would cause group-III metals, especially indium, to be deposited on the surface of the substrate, but not incorporated into the crystal lattice. It was found that higher temperatures were required to produce photoluminescent materials in this high-pressure reactor, than in comparable low-pressure growths. The reasons for this are not well understood.The samples were all grown on sapphire substrates with a previously grown HVPE GaN layer on top. Preliminary work was performed on the buffer/nucleation layer. The current buffer/nucleation layer is still not completely epitaxial, and this is thought to be a major limiting factor on the current quality of the material and device-like structures in this work. However, this work significantly improved the buffer/nucleation layer, from its initial state, and has identified several important factors for improving the quality of the buffer layer and ultimately, opto-electronic devices.Also, photoluminescence over growth pressure and NH3 partial pressure was investigated. The samples in this thrust were grown from 1.5 bar(a) to 2.5 bar(a) or 0.55 to 0.91 bar(a) NH3 partial pressure. The results indicate that the photoluminescent efficiency of the samples increased, as their growth pressure increased.This work concludes with a preliminary recipe for photoluminescent InGaN, at super-atmospheric pressures and initial data, relating photoluminescence to specific process variables. The current growth recipe is given at the conclusion of this work. This recipe is not yet commercial quality; its photoluminescent intensity is not high enough (low IQE), and the growth mode, in the produced samples, is not epitaxial enough. The two issues are thought to be highly related.

Genre

masters theses

Subjects--Topics

Materials science
Electrical engineering
Nanotechnology

Degree

M.S.

Keywords

HP-MOCVD
III-Nitrides
Ingan
MOCVD
Pressure
Quantum Efficiency

Subject Area

Electrical Engineering

Advisor(s)

Stokes, Edward

Committee Members

Ebong, Abasifreke
Kakad, Yogendra

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2019.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Conway_uncc_0694N_12080

Permalink

http://hdl.handle.net/20.500.13093/etd:1977