Measurement of the optical band gap and crystal-field splitting in wurtzite CdTe

CdTe nanocrystals embedded in a sodium borosilicate matrix, obtained by a sol-gel process, present a wurtzite (hexagonal) structure. Low-temperature photoluminescence and absorption spectra are measured for samples containing bulklike nanocrystals large enough to suppress confinement effects. Thus, the fundamental free-exciton gap and the splitting between the A (Gamma(9)(v) - Gamma(7)(c)) and B (Gamma(7)(v) - Gamma(7)(c)) excitons of bulk wurtzite CdTe are measured. We find E(g)(A) = 1653 +/- 1 meV and E(g)(A) - E(g)(B) = 46.5 +/- 1.0 meV, which corresponds to a crystal-field splitting Delta(cr) = 71.6 +/- 1.5 meV.