Electronic structure and properties of nitride semiconductor compound alloys

Linear Combination of Atomic Orbitals (LCAO) electron band structure calculations are used to examine the influence of common defect structures that may arise as artifacts during the growth of InN. For 1.9 eV band-gap InN, the formation of indium rich non-stoichiometric InN leads to the creation of a lower band-gap material, due to the single substitution of indium atoms on nitrogen sites. Optical absorption at energies as low as 0.20 eV for non-stoichiometric InN is calculated, consistent with recent observations of the optical absorption spectrum. The role of oxygen alloying is also examined, and the ternary semiconductor InOyN1-y, with y similar to 0.1 is identified. It is also found that the presence of this concentration of 0 atoms in InN decreases the band-gap energy. Optical absorption as low as 1.19 eV can be evident, while exciton emissions are found to vary in energy over the range 0.84 - 1.01 eV. This work suggests that oxygen alloys play no role in causing any supposedly smaller band-gap of InN than the observed 1.9 eV.