Common-anion rule and its limits: Photoemission studies of CuIn/sub x/Ga/sub 1-//sub x/Se/sub 2/-Ge and Cu/sub x/Ag/sub 1-//sub x/InSe/sub 2/-Ge interfaces

Synchrotron-radiation photoemission data show that the valence-band discontinuities of CuIn/sub x/Ga/sub 1-//sub x/Se/sub 2/-Ge and Cu/sub x/Ag/sub 1-//sub x/InSe/sub 2/-Ge interfaces are independent of x within the experimental accuracy of 0.1 eV. We argue that this result is consistent with the Wei-Zunger explanation of the breakdown of the common-anion rule, which is based on a substantial role of the cation d states in determining the valence-band-edge position.