Quantitative study of atomic ordering inGa0.5In0.5P thin films byP31nuclear magnetic resonance

We use $^{31}\mathrm{P}$ nuclear-magnetic-resonance (NMR) spectra to measure the degree of cation ordering in thin films of the semiconductor alloy ${\mathrm{Ga}}_{0.5}$${\mathrm{In}}_{0.5}$P grown by organometallic vapor-phase epitaxy. We show that the five possible ${\mathrm{Ga}}_{\mathit{n}}$${\mathrm{In}}_{4\mathrm{\ensuremath{-}}\mathit{n}}$P clusters in ${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{In}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$P give rise to resolved NMR lines under magic-angle spinning, allowing a determination of the degree of cation ordering from the relative areas of the five lines. The ordering is shown to be weak (order parameter \ensuremath{\le}0.6) even in films that appear highly ordered in transmission electron microscopy.