Effect of GaAs surface treatments using HCl or (NH₄)₂S_X solutions on the interfacial bonding states induced by deposition of Au

The chemical bonding nature of the Au/GaAs interface has been investigated using monochromatic X-ray photoelectron spectroscopy (XPS), with an initially different GaAs surface obtained by HCl cleaning or S-passivation. The composition, chemical bonding state, and thickness of the interface were obviously dependent on the preparation of GaAs surface prior to Au-deposition. The interface region of Au/S-passivated GaAs was more uniform than Au/HCl-cleaned GaAs. In particular, surface bonding states such as As - O and As - S prior to Au-deposition were changed to Ga - O and Ga - S bonding due to the energy released from the deposition of Au, resulting in a combination of resultant As and Au. These bonding transitions were observed to occur at As - O/GaAs and As - S/GaAs interfaces. The bonding-layer distributions of the interfaces induced from non-destructive angle-resolved XPS measurements were Au/Au,As - O/As - Au/Ga - O/Ga - As in the Au/HCl-cleaned GaAs, and Au/As - Au/As - S,Ga - S/GaAs in the Au/S-passivated GaAs.