We report on the influence of the chemical etching in the step bunching formation on GaAs (100) 0.2 degrees off and GaAs (100) 2 degrees off to ward < 010 > surfaces after the oxide desorption process of the substrates at high temperatures under an H-2 ambient. The step bunches were observed by in-air atomic force microscopy. Our results reveal that step bunches were formed only on chemically etched samples desorbed under an As-4 overpressure using H-2 as the carrier. When GaAs substrates without chemical etch were deoxidized the step bunches were not observed in despite of the H-2/As-4 presence. From the results we conclude that the chemical etching strongly influence the step bunching formation. (c) 2006 Elsevier B.V. All rights reserved.