We report, for the first time, a direct relationship between the composition fluctuation on the ternary layer grown by atmospheric pressure metalorganic vapor-phase epitaxy (AP-MOVPE) and the pulsed character of high-vapor-pressure metalorganic (MO) flows. We show that the grwoth rates of GaAlAs and GaInAs layers, grown with trimethylgallium (TMG) and triethylgallium (TEG) sources, are of tens of angstrom per bubble for the methyl case and a few angstrom for the ethyl one.