X-ray photoelectron spectroscopy study of GaAs (001) surface thermocleaning prior to molecular beam epitaxy

X-ray photoelectron spectroscopy has been performed in order to investigate the encapsulent effect of an oxide layer, grown at the end of the chemical etching procedure, on the annealing behaviour of GaAs (001) substrates prior to M.B.E. growth. The oxide layer makes the surface unable to react with arsenic molecules until the desorption of the gallium oxide around 570 °C, preventing the surface against arsenic desorption below this temperature. Otherwise, if unoxidized substrates are used, annealing must be performed under an arsenic flux from 150 °C upwards to avoid the formation of an arsenic depleted surface.