LOW-TEMPERATURE CHLORINATION OF GAAS(100)

The chemisorption and the reaction of chlorine and hydrogen chloride o n the GaAs(100)-4 x 6 surface at 110 K are investigated using soft X-r ay photoelectron spectroscopy which employs synchrotron radiation. At low exposures, Cl-2 and HCl dissociate and preferentially adsorb on th e As atom, which causes As-Ga bond breakage to initiate chlorination o f the Ga atom. AsxCl is proposed to form at initial chlorination, in w hich the Cl atom is bonded to a high coordination site. Subsequently, various AsClx and GaClx (x = 1, 2, and 3) species are formed on the Ga As surface, and their corresponding chemical shifts are assigned. At h igh exposures, chlorination of the GaAs surface is saturated, and the surface is mainly covered with physisorbed Cl-2 and HCl molecules. Syn chrotron radiation on the chlorinated GaAs surface stimulates both the photodesorption of Ga and As chlorides and the photodissociation of p hysisorbed Cl-2 molecules. A potential route for anisotropic cryogenic etching of the GaAs surface by the chlorine-containing compound under photon irradiation is discussed.