1.5-μm emission of naturally-oxidized InN crystals grown by MOVPE

Photoluminescence (PL) spectrum of a naturally-oxidized InN sample has been investigated. The PL-peak wavelength locates at around 1.53 μm, which is by 250-300 nm shorter than that of an intrinsic InN. In addition to this PL peak shift of the InN crystals (corresponding bandgap variation) their quality seems to be improved from the analysis of PL spectra. The naturally-oxidized layer is found to have the original lattice structure of InN from X-ray diffraction measurements. The 8-20 % of oxygen atoms has been evaluated to be incorporated in the InN layer by the energy dispersive X-ray spectroscopy. The PL spectra have been affected by temperature. While a PL-peak intensity increases with temperature decrease, a PL-peak shifts toward the longer wavelength. Such red-shift tendency is opposite to the case of other III-V compounds. This anomalous temperature effect has been proved from variation of PL spectra with time after excitation.