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Title: Ab initio investigation of GaN and related materials
Author: Chisholm, J. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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GaN is shown to be a highly important semiconductor material for the fabrication of electronic devices such as light emitting diodes, laser diodes and field effect transistors. In the main calculations are carried out using density functional theory. The details of the particular implementation used are given in chapter 2. This methodology is then used to investigate the formation energy of basal plane stacking faults in a selection of wurtzite materials, namely; GaN, AlN, InN, BeO and ZnO. The investigation explores the reasons for the range of stacking fault energies across the materials. This thesis also addresses the question of the influence of impurity doping on the formation of stacking faults in GaN. Experimental evidence has shown that the density of basal plane stacking faults is higher in silicon doped GaN compared to undoped GaN. Present calculations confirm that silicon encourages the formation of cubic material. The influence of carbon, magnesium, indium and aluminium is also investigated as is the relation between the wurtzite-sphalerite structural energy difference and the bonding characteristics of doped GaN. A pair potential model for the group-III nitrides is developed in chapter 4. The model is used to investigate the incorporation of indium and aluminium into GaN and the interaction between native defects and planar defects which requires the use of large supercells. It is shown that native defects have a positive binding energy to all three boundary structures considered and that the binding energy is highest for interstitial defects. Work in this thesis also investigates magnesium and carbon acceptors in GaN. The influence of indium and aluminium on the solubility and on the depth of the acceptor level is investigated in order to determine whether such elements can improve the properties of the acceptors. Chapter 6 looks at the formation energy and the electrical behaviour of metal impurities in GaN.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available