Light Emitting Diodes and Dilute Magnetic Semiconductors in the III-Nitride Materials System

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Title: Light Emitting Diodes and Dilute Magnetic Semiconductors in the III-Nitride Materials System
Author: Reed, Mason Jacob
Advisors: Ray Benson, Committee Member
Hans Stadelmaier, Committee Member
Salah Bedair, Committee Co-Chair
Nadia El-Masry, Committee Chair
Abstract: The purpose of this research has been to produce novel light emitting diodes in the III-nitride materials system via metal organic vapor phase epitaxy. Three distinct types of devices were grown: 1) blue light emitting diodes with a peak wavelength of 445 nm were grown on sapphire substrates, 2) blue light emitting diodes were grown on ruby substrates to produce dual wavelength light emitters with peak wavelengths of 430 nm and 694 nm, and 3) ultraviolet light emitting diodes with a quaternary active region with a peak wavelength of 340 nm were grown on sapphire substrates. The diodes' characteristics are examined and iteratively improved based on feedback from characterization. Modifications to the metalorganic chemical vapor deposition system's physical configuration and growth parameters have also been employed to improve material properties. The dual wavelength light emitting diodes have been produced as a first step towards the realization of a monolithic white light emitting diode for potential use in solid state lighting applications. These dual wavelength devices were grown on chromium doped sapphire substrates (also known as ruby). The high energy photons originating in the III-nitride active region photoexcite chromium atoms within the ruby substrate which subsequently emit red photons. In this manner a compact dual emitter of both red and blue photons is realized. The quaternary ultraviolet light emitting diodes were demonstrated as a potential path towards more efficient short wavelength emitters in the group III-nitride materials system. The incorporation of a small percentage of indium has been shown to increase the radiative recombination efficiency of AlGaN layers due to induced carrier localization at indium fluctuations. Ultraviolet light emitting diodes emitting at a peak wavelength of 340 nm were demonstrated using this approach.An investigation of the ferromagnetic properties Mn-doped GaN dilute magnetic semiconductors on the material's Fermi energy was also made. It was found that the occupancy of the deep manganese acceptor level must be controlled through Fermi energy engineering to achieve ferromagnetic GaN:Mn.
Date: 2005-08-05
Degree: PhD
Discipline: Materials Science and Engineering

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