Different ammonia flow rates were used during temperature ramping up to 1050degreesC after InGaN/GaN multiple quantum wells (MQWs) were grown at 820degreesC. Temperature-dependent photoluminescence (PL) as well as time-resolved PL (TRPL) spectra were measured and higher optical efficiency was obtained when higher ammonia flow rates were used. The effects of ammonia flow on the optical properties of InGaN/GaN multiple quantum wells were attributed to different indium content redistribution. At lower ammonia flow, In-rich regions became more uniform while the number of the In-rich regions decreased as a result of the disappearance of some In-rich regions with less In-rich regions. We ascribed enhancement of desorption of indium atoms to the lower ammonia flow. (C) 2003 Elsevier Science B.V. All rights reserved.