Using in situ spectral reflectance (SR), we investigated the growth procedures of InAs layers on the As-stabilized and As-depleted GaAs buffer layers in low-pressure metalorganic chemical vapor deposition. The time-transient SR signals along the [I 10] direction were analyzed at several wavelengths. When trimethylindium (TMIn) was supplied, we observed that the loss of excess As layer and the growth of InAs layer occur simultaneously. The loss of some As atoms in the excess layer and the second layer during an AsH3-off step was also observed. In addition, SR signal showed that the surface structure changed for a few seconds after TMIn supply was stopped. We also report the InAs growth on InGaAs buffer layer in a similar manner. (c) 2006 Elsevier B.V. All rights reserved.