Atomic Force microscopy was used to investigate the morphology of GaAs(001) layers deposited by molecular beam epitaxy using a non conventional growth method that involves the supply of a few monolayers of gallium (the arsenic cell is shuttered) followed by the annealing of the surface under an arsenic ux (the gallium cell is shuttered). When the silicon shutter is opened and closed together with the gallium one, this particular growth mode allows the silicon atoms to be incorporated into the arsenic sites and p-type GaAs(001) layers can be obtained. Several sets of samples were grown and analyzed in order to better understand the microscopic growth mechanisms of this kind of layers and minimize the number and size of the structural defects that are characteristic of this peculiar technique.