Low temperature annealing of GaMnAs layers has been established as a standard tool for improvement of their magnetic and transport properties. We report on a strong enhancement of the annealing efficiency achieved by chemical removal of the Surface oxide layer during the annealing of GaMnAs layers. These data together with the results of angular resolved X-ray photoemission experiments are used for elucidation of processes during the annealing of GaMnAs layers. (c) 2007 Elsevier B.V. All rights reserved.