Experimental Consideration of Optical Band-Gap Energy of Wurtzite InN

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Wurtzite InN films were grown on a thick GaN layer by metalorganic vapor phase epitaxy (MOVPE). Growth of a (0001)-oriented single crystalline layer was confirmed by Raman scattering with polarized geometry, X-ray diffraction, and reflection high-energy-electron diffraction. In the growth, an extremely high V/III ratio of around 700000 was used to suppress inclusion of metal-indium. We observed at room temperature strong photoluminescence (PL) at 0.75 eV as well as a clear absorption edge at 0.7–1.0 eV. In contrast, no PL was observed, even at high power excitation of 0.6 MW/cm2 at ${\sim}1.9$ eV, which had been reported as the band-gap in absorption experiments on single crystalline films grown by microwave-excited MOVPE and poly-crystalline ones. Careful inspection strongly suggests that a wurtzite InN single crystal has a true band-gap energy of 0.7–1.0 eV, and the discrepancy between this and previous data could be due to the difference in the crystallinity of the materials measured.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-04-15