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

Abstract

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 (${\mathrm{\ensuremath{\Gamma}}}_{9}^{\mathit{v}}$-${\mathrm{\ensuremath{\Gamma}}}_{7}^{\mathit{c}}$) and B (${\mathrm{\ensuremath{\Gamma}}}_{7}^{\mathit{v}}$-${\mathrm{\ensuremath{\Gamma}}}_{7}^{\mathit{c}}$) excitons of bulk wurtzite CdTe are measured. We find ${\mathit{E}}_{\mathit{g}}^{\mathit{A}}$=1653\ifmmode\pm\else\textpm\fi{}1 meV and ${\mathit{E}}_{\mathit{g}}^{\mathit{A}}$-${\mathit{E}}_{\mathit{g}}^{\mathit{B}}$=46.5\ifmmode\pm\else\textpm\fi{}1.0 meV, which corresponds to a crystal-field splitting ${\mathrm{\ensuremath{\Delta}}}_{\mathrm{cr}}$=71.6\ifmmode\pm\else\textpm\fi{}1.5 meV. \textcopyright{} 1996 The American Physical Society.