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https://hdl.handle.net/2142/21933
Description
Title
Optical properties of III-V semiconductors
Author(s)
Kisting, Scott Robert
Issue Date
1991
Doctoral Committee Chair(s)
Bohn, Paul W.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Language
eng
Abstract
A GaAs-Al$\sb{0.22}$Ga$\sb{0.78}$As heterostructure was prepared and used as a multimode optical waveguide in order to measure the sub bandgap energy- and temperature-dependent refractive index of GaAs. Propagation constants for the individual modes were measured by exciting one mode at a time using a real-space diffraction grating coupler. The resulting eigenmode distributions were used to obtain the refractive index of GaAs at a matrix of sub bandgap photon energies (1.40 eV $<$ h$\nu <$ 1.50 eV) and temperatures (40 K $<$ T $<$ 300 K). Values for the temperature dispersion (dn/dT) at each photon energy, and the extrapolated refractive index at T = 0 K are presented. For the energy dispersion results, Sellmeier parameters including the long wavelength dielectric constant at each temperature are presented. The dominant error source in these measurements was uncertainty in the angular placement of the sample.
In order to exploit the inherent sensitivity of modulation spectroscopy to measure the extrinsic contribution to the Urbach tail, the electro-optic tuning of a Ti:sapphire laser was investigated using a potassium dideuterophosphate (KD*P) crystal. The limited success in tuning and producing wavelength modulated electromagnetic radiation is discussed, and a model is presented for the observed laser output. Suggestions for the improvement of the studied modulation system are also given.
Another phase of this project was to quantitate disorder in III-V semiconductor crystal lattices using Raman scattering in the backscattering geometry. The source of disorder in these materials was from a reactive ion etch plasma. The goal of this work is to use Raman scattering on a variety of etched epitaxial layers of GaAs and InP to diagnose etch induced lattice disorder. The desire was to minimize the disorder in the sample, while maintaining a reasonable amount of etch anisotropy in the desired structures. The Raman depolarization ratio of the longitudinal phonon can be used to diagnose the amount of disorder in the epitaxial layer. Using phonon scattering, reactive ion etch conditions which led to a compromise between effective etch profiles and minimal etch damage were identified for GaAs and InP.
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