Work on the analysis by in situ monitoring using a 980 nm laser reflectometer of parasitic deposition during MOVPE growth of GaAs/AlGaAs layers in an Aix-2400 planetary reactor is presented here. Real-time growth rates for parasitic deposition have been measured for the first time. The parasitic deposition does not have a linear growth rate during growth of the n-DBR layers in a VCSEL structure. During the early stages of buffer growth and subsequent baking experiments at 850degreesC, a reflectance signal was detected from the substrates indicating significant penetration through the deposit at this wavelength. (C) 2003 Elsevier B.V. All rights reserved.