Linear combination of atomic orbitals 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 In(x)A(l-x)N or InxGa1-xN interfacial layers results in lower band-gap material. Exciton emissions at energies as low as 0.765-0.778 eV for In(x)A(1-x)N, and as low as 0.50-0.82 eV for InxGa1-xN are calculated, which are consistent with the recent observations of luminescence in InN. Optical absorption features are shown to also occur at energies that would interfere with band-gap measurements. The role of oxygen alloying was also examined, and the ternary semiconductor InOyN1-y with y similar to 0.1 was identified. It was also found that the presence of this concentration of O atoms in InN decreases the band gap energy. Optical absorption as low as 1.19 eV can be evident, while exciton emissions were found to vary in energy over the range 0.84-1.01 eV. This work suggests that oxygen alloys play no role in raising any supposedly smaller band gap of InN to the observed 1.9 eV. (C) 2004 Elsevier B.V. All rights reserved.