Phase separation in In x Ga 1‐x N (0.10 < x < 0.40)

We have performed micro-photoluminescence (µ-PL) mapping of InGaN films with thickness up to 300 nm with a large gradient of In concentration in a lateral direction (from 10% to 40%), grown by plasma-assisted molecular beam epitaxy atop a 1.8-µm-thick GaN() buffer deposited on a c-Al2O3 substrate. The µ-PL spectra measured at various points with different average composition show almost identical emission bands with fixed wavelength ranges: 490-540 nm (green band), 550-590 nm (orange band), and 600-660 nm (red band). This behavior implies emergence of at least three phases with fixed In contents, which are nearly independent of the average film composition and the variation of the growth temperature. The variation of the average composition of the InGaN ternary alloy results in redistribution of the band intensities that can be explained by redistribution of the relative volumes of the spatially separated phases. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)