Hydrogen-induced contamination of III-V compound surfaces

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Abstract
Specific examples are reported from the study of H/GaAs(110), H2+/GaAs(110), and H/InP(110) systems in which the initially clean surfaces, prepared by cleavage in ultrahigh vacuum, became contaminated through enhanced or displacive reactions involving excited hydrogen. They show that elements forming volatile hydrides can be displaced by atomic or ionized hydrogen onto the sample surface from those parts of the ultrahigh vacuum chamber (walls, equipments) on which they are present. The surface electronic properties were followed by photoemission yield spectroscopy. Comparison with the clean systems shows that the main effects of contamination on these properties concern (i) an irreproducible variation of the ionization energy during the adsorption stage at the lower exposures, and (ii) the nonobservation of the yield quenching phenomenon which appears during the dissociation stage upon heavy hydrogenation in the clean cases.