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Title:Semiconductor electronic band alignment at heterojunctions of wurtzite aluminum nitride, gallium nitride, and indium nitride
Author(s):Martin, Gregory Allen
Doctoral Committee Chair(s):Wolfe, J.P.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
Abstract:In this thesis the band alignments for wurtzite (0001) heterojunctions of AlN, GaN, and InN semiconductors are measured by x-ray photoemission spectroscopy. The bands alignments are all found to be Type I, and the valence-band discontinuities are found to be:(UNFORMATTED TABLE OR EQUATION FOLLOWS)$$\vbox{\halign{#\hfil&&\qquad #\hfil\cr &$\rm\Delta E\sb{v}$\ (eV)\cr\cr GaN on AlN &0.60 $\pm$ 0.24\cr AlN on GaN &0.57 $\pm$ 0.22\cr InN on GaN &0.93 $\pm$ 0.25\cr GaN on InN &0.59 $\pm$ 0.24\cr InN on AlN &1.71 $\pm$ 0.20\cr AlN on InN &1.32 $\pm$ 0.14\cr}}$$(TABLE/EQUATION ENDS)
Forward-backward growth asymmetries are found for InN$\vert$GaN and InN$\vert$AlN, and highlight the importance of lattice mismatch and its influence on band alignment. The dielectric midgap energy is affected by lattice mismatch strain to a small degree, but in the opposite direction as observed in the experimental results. The strain-induced piezoelectric effect would provide effects of the correct sign, but an explicit overlayer thickness dependence is not observed: The model of pseudomorphic strain is rejected for InN$\vert$GaN and InN$\vert$AlN as expected for the exceedingly large lattice mismatches, but pseudomorphic strain is not ruled out for GaN$\vert$AlN. Thermal mismatch strain is rejected as a significant factor. In general there is insufficient knowledge of strain conditions at heterojunctions of AlN, GaN, and InN to provide quantitative strain corrections to the observed valence-band discontinuities. A bonding model assumes the lattice mismatch is accommodated by dislocations and dangling bonds at the interface. The dangling bonds are viewed as dipole corrections to the ideal lattice-mismatched heterojunction, and the dipole model accounts for the signs and trends of the observed forward-backward asymmetries but the model values are an order of magnitude too small. Using rough approximations for strain and dangling bond corrections the "bulk" valence-band discontinuities are estimated as GaN$\vert$AlN $\approx$ 0.7 eV, InN$\vert$GaN $\approx$ 0.76 eV, and InN$\vert$AlN $\approx$ 1.51 eV. These values satisfy transitivity to well within experimental and estimation uncertainties. Tabulations of x-ray photoemission values for core-level energies with respect to valence band edges for wurtzite AlN, GaN, and InN are presented.
Issue Date:1996
Rights Information:Copyright 1996 Martin, Gregory Allen
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712370
OCLC Identifier:(UMI)AAI9712370

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