| Abstract [eng] |
Properties of materials are strongly influenced by the presence of defects and impurities. This effect is particularly strong in the case of semiconductor materials. As these materials are widely used in the production of various electronic devices (lasers, light-emitting diodes), their theoretical analysis is of utmost importance. Gallium nitride (GaN) is a particularly important semiconductor that enabled the creation of high-brightness LEDs in the blue-UV region of the spectrum. Recently, using experimental evidence, a hypothesis was put forward which states that nitrogen vacancies and gallium-nitrogen divacancies present in GaN act as non-radiative recombination centers, limiting the efficiency of radiative processes in optoelectronic devices. However, currently there is no consensus regarding the defects that cause non-radiative recombination in GaN. The main goal of this work was to analyse the electronic structure of hexagonal wurtzite crystal structure GaN having a gallium-nitrogen divacancy and either confirm or deny the hypothesis that this divacancy can act as an efficient recombination center. Density functional theory was used to perform calculations from first principles on a supercell of 126 atoms. This was done using VASP software suite. Spin-polarized calculations were performed using the HSE form of the hybrid functional. The main results of this work involve a formation energy diagram of the divacancy complex in different charge states (q = +1; 0; -1; -2) and an energy level diagram of a supercell with a neutral (q = 0) divacancy, for which an approximate excitation energy between two defect levels inside the band gap was calculated. The results indicate that the divacancy defect has similar properties to the VGa-ON complex, which was already shown to behave as an inefficient non-radiative recombination center in GaN. |
