We have used low temperature photoluminescence and atomic force microscopy to study the growth, by chemical beam epitaxy, of self-assembled InAs/InP quantum dots. By modifying the procedure for capping the dots we have been able to control their emission energy by adjusting their height. This process relies on the As/P exchange process that occurs when an InAs surface is exposed to a phosphorus flux. This exchange is shown to occur for both continuous and discontinuous capping procedures. (C) 2003 Elsevier B.V. All rights reserved.