"Impurezas e defeitos nativos em nitretos do grupo-III cúbicos" (Portuguese),
L.E. Ramos, PhD. thesis (2002), Universidade de São Paulo - Instituto de Física , São Paulo, Brazil.

Group-III nitrides (BN, AlN, GaN e InN) are commonly used in optoelectronic devices in the range of wavelengths from blue to ultraviolet such as lasers, light emitting diodes, transistors, photodetectors, advertisement panels and as cover material in abrasive tools. The III-nitrides present in general a large tolerance to high temperatures, support high electric-current injections in devices, are mechanically robust and form cation-cation-nitrogen alloys which allows the fundamental gap engineering, the latter required in optical applications. The most stable and used structure in applications of group-III nitrides is the wurtzite, except in BN for which the zincblende structure is the most stable. Recently AlN, GaN and InN have been synthesized in their zincblende phase which, in principle, offers advantages with respect to the wurtzite one such as a higher lattice symmetry. Semiconductor crystals present in general disarrays or defects (vacancies, dislocations and so on) as well as certain amount of impurities. In order to obtain the required electronic properties in the semiconductor material, it is an usual procedure to introduce impurities by means of the process named doping. Because the synthesis of the zincblende phase of the group-III nitrides AlN, GaN and InN is recent, we present in the following a study of the electronic and structural properties of the cubic nitrides applying the density-functional theory (DFT), supercells in the local density approximation (LDA) and generalized gradient approximation (GGA). We combine ab initio and statistical mechanics to study defects in the ternary alloys Al_{x}Ga_{1-x}N taking as an example the nitrogen vacancy in several charge states. A study of substitutional group-IV impurities in AlN and GaN (C, Si, and Ge), which are traditionally applied in semiconductor technologies is presented as well as for group-V impurities (P, As, and Sb), covering impurity levels in the fundamental gap, lattice geometry and lattice energy relaxation. We study more detailedly the carbon impurity substitutional on the nitrogen site in BN, AlN, GaN and InN, applying supercells up to 2744 atoms, in order to investigate the effect of the impurity-impurity interaction due to the use of the supercell approximation as well as optical properties (Franck-Condon shifts, absorption and emission levels), lattice relaxation energies and defect levels. Since carbon has shown to be a promising dopant material, we analyze also the stability of complex defects which incorporate two atoms of carbon on substitutional sites and the so called split-interstitial configurations.