Valence-band structure ofCuGaxIn1−xS2alloys

We report measurements of the valence-band structure in $\mathrm{Cu}{\mathrm{Ga}}_x{\mathrm{In}}_{1-x}{\mathrm{S}}_2$ alloys which resolve the recent controversy regarding the valence-band structures of CuGa${\mathrm{S}}_2$ and CuIn${\mathrm{S}}_2$. We find that (i) the spin-orbit splitting is negative in CuIn${\mathrm{S}}_2$, (ii) the crystal-field splitting dominates the valence-band structure in CuGa${\mathrm{S}}_2$, and (iii) the vanishing crystal-field splitting in CuIn${\mathrm{S}}_2$ results from an accidental cancellation of three competing phenomena.