Absorption and photoluminescence features caused by defects in InN

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 1.9eV band gap InN, the formation of indium rich In_xAl_1-xN or In_xGa_1-xN interfacial layers results in lower band-gap material. Exciton emissions at energies as low as 0.765-0.778eV for In_xAl_1-xN, and as low as 0.50-0.82eV for In_xGa_1-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 InO_yN_1-y with y∼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 1.19eV can be evident, while exciton emissions were found to vary in energy over the range 0.84-1.01eV. This work suggests that oxygen alloys play no role in raising any supposedly smaller band gap of InN to the observed 1.9eV.