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 (${\mathrm{\Gamma }}_9^{\mathit{v}}$-${\mathrm{\Gamma }}_7^{\mathit{c}}$) and B (${\mathrm{\Gamma }}_7^{\mathit{v}}$-${\mathrm{\Gamma }}_7^{\mathit{c}}$) excitons of bulk wurtzite CdTe are measured. We find ${\mathit{E}}_{\mathit{g}}^{\mathit{A}}$=1653±1 meV and ${\mathit{E}}_{\mathit{g}}^{\mathit{A}}$-${\mathit{E}}_{\mathit{g}}^{\mathit{B}}$=46.5±1.0 meV, which corresponds to a crystal-field splitting ${\mathrm{\Delta }}_{\mathrm{cr}}$=71.6±1.5 meV. © 1996 The American Physical Society.