Photoemission studies of the Cu-InP(110) interface

The atomic and electronic structure of Cu-($n$-type) InP(110) interface has been studied by soft-x-ray photoemission spectroscopy and Auger spectroscopy for copper coverages ranging from 0.7 to 80 Å. By monitoring the evolution of the P $2p$ and In $4d$ core-level spectra and the change of the Cu $3d$ level, which is degenerate with the substrate valence band, we provide evidence of strong intermixing taking place at the interface. A strong outward diffusion of phosphorous into the copper overlayer and indium segregation at the surface have been observed. A splitting of the phosphorous $L_{2,3}\mathrm{VV}$ Auger line has been observed for Cu coverages higher than 8 Å. This splitting, similar to that observed for silicides, provides evidence of bond formation between Cu and P. On the basis of the P $2p_{\frac{3}{2}}$ line shift, a Schottky-barrier height of 0.6 eV has been established.