Thesis

Computational investigation of InGaN alloys over the full composition range

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13691
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Abstract
  • The properties of InGaN alloys are important for many applications in optoelectronics, since the fundamental band gap of this material system spans the visible range. Calculating properties, particularly for InN, is theoretically challenging, especially obtaining accurate values for the band gap. We have developed a semiempirical parameterization for the simulation of (In,Ga)N using the density functional based tight binding method (DFTB), where the band gaps of InN and GaN have been empirically adjusted to match experiment. This is the first application of this method to In containing materials. We demonstrate the performance of this method by calculating a range of properties for both compounds and also their alloy for a range of crystal structures (wurtzite, zincblende and, for the pure compounds, rocksalt). There are several methods to model alloys of these materials, here the virtual crystal approximation and the cluster expansion method been used to study the alloy system of InGaN. While 8, 16 atom supercells are commonly used for cluster expansions, in this work these results are critically compared against the larger 32 atom cell, the effect of the ensemble used to simulate the alloy is also investigated by using both the Strictly Regular Solution and Generalised Quasi-Chemical approximations to provide limiting cases around the experimental conditions of Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) alloys.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1028836

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