InAlN epilayers deposited on thick GaN buffer layers grown by metalorganic chemical vapour depostion (MOCVD) revealed an auto-incorporation of Ga when analysed by wavelength dispersive x-ray (WDX) spectroscopy and Rutherford backscattering spectrometry (RBS). Samples were grown under similar conditions with the change in reactor flow rate resulting in varying Ga contents of 12–24%. The increase in flow rate from 8000 to 24000 sccm suppressed the Ga auto-incorporation which suggests the likely cause is from residual Ga left behind from previous growth runs. The luminescence properties of the resultant InAlGaN layers were investigated using cathodoluminescence (CL) measurements.