Luminescence studies in In_xGa_(1-x)N epitaxial layers with differentindium contents

摘要

The optical properties of In_χGa1-χN epitaxial layers (x = 0.02, 0.04, 0.11, 0.15, 0.30 and 0.33) grown by metalorganic chemical vapor deposition (MOCVD) have been investigated by temperature-dependent photoluminescence (PL) measurement. The surface morphologies of InGaN samples are studied by scan-ning electron microscopy (SEM) images. The PL feature at 12 K has shown an increase in full-width at half-maximum (FWHM) with increasing In content. An anomalous S-shaped temperature dependence of the PL peak energy exhibited by InGaN films with higher In content enabled the evaluation of the exci-ton localization energy. The broadened FWHM and S-shaped emission shift are attributed to larger com-positional fluctuation due to compositional inhomogeneity of In. Additionally, the luminescence mechanism relating to the phase separation has to be considered for the much larger FWHM value and the pronounced S-shaped behavior for the InGaN samples with In content of 0.30 and 0.33.