Photoemission Studies of CdTe

By correlating structure in the CdTe energy distributions of the photoemitted electrons with structure in the optical data, we determine the absolute energies of the initial and final states for the transitions associated with peaks in the reflectivity at 6.8 and 7.6 eV and shoulders at 5.8 and 8.7 eV. It is shown that the structure in the energy distributions results from a mixture of direct and nondirect transitions. The direct transitions allow us to locate the conduction-band states ${\Gamma }_{15}$ and ${\Gamma }_1$ at 5.8 and 8.7 eV above the valence-band maximum, the uppermost valence band along the zone edge $W$ to $K$ at -1.3 eV, and the second conduction band along the zone edge $W$ to $K$ at 5.3 eV. The nondirect transitions are due primarily to a peak at -1.9 eV in the valence-band effective density of states and a gentle peak at 6.2 eV in the conduction-band effective density of states. A deep valence band, tentatively identified as the cadmium $4d$ band, has been located at 10.3 eV below the valence-band maximum.