Structural and optical properties of indium nitride (InN) layers grown by high-pressure chemical vapor deposition (HPCVD) on sapphire and GaN epilayers have been studied. HPCVD extends processing parameters beyond those accessible by molecular beam epitaxy and metal organic chemical vapor deposition, enabling the growth of epitaxial InN layers at temperatures as high as 1150 K for reactor pressures around 15 bars, leading to vastly improved material properties. InN layers grown on GaN(0002) epilayers exhibit single-phase InN(0002) x-ray diffraction peaks with full width at half maximum (FWHM) around 430 arc sec. Optical characterization of the InN layers by infrared (IR) reflectance reveals free carrier concentrations in the low to mid-10(+19)-cm(-3) and optical dielectric function epsilon(infinity)=5.8. The optical properties in the visible and near IR spectral ranges were analyzed by transmission spectroscopy, showing an absorption edge around 1.5 eV. The shift of the absorption edge correlates with deviations in the InN stoichiometry, indicating that the understanding and control of the point defect chemistry of InN is critical for improved material properties. (c) 2006 American Institute of Physics.