Photoemission studies ofCuInSe2andCuGaSe2and of their interfaces with Si and Ge

We studied the electronic structure of two fundamental components of the $A^{\mathrm{I}{B}^{\mathrm{III}{X}_2^{\mathrm{VI}}}}$ family of semiconductors by synchrotron-radiation photoemission. The experiments investigated the clean-surface density of occupied states, the Cu d-band satellites with photoemission resonant behavior at the Cu 3p optical absorption threshold, and the absolute energy position of the valence-band edges, $E_v$. In particular, we estimated the $E_v$ terms (relative to the top of the valence band of Ge), which can be used to determine the band discontinuities of heterojunctions involving these materials. As an example, the $E_v$ term obtained for ${\mathrm{CuInSe}}_2$ was used to predict the conduction-band discontinuity of the ${\mathrm{CuInSe}}_2$/CdS heterojunction solar cell.