Photoluminescence iSe under hydrostatic pressure

We report on low temperature measurements of the pressure dependence of the photoluminescence (PL) associated with (Formula presented) in ZnSe performed in a diamond anvil cell. Two sharp emission peaks at ∼2.36 eV, labeled L and (Formula presented), show a weak redshift under pressure with rapidly decreasing peak intensities. These results, together with the excitation energy and temperature dependence of the PL at 1 bar, allow for a critical examination of previous models proposed for these optical transitions. The PL data are discussed within the framework of conventional crystal-field theory based on the Racah and crystal-field parameters B, C, and Δ(=10Dq). From this analysis, the normalized energy E/B is determined as a function of the normalized crystal field parameter Dq/B. Thus quantitative estimates for the enhancement in the p-d hybridization with pressure (evident in the line-shape profiles of the spectra) are deduced. The energy separation between L and (Formula presented) decreases continuously for modest pressures (∼1 GPa), and raises questions about the role of spin-orbit coupling in accounting for the splitting of this emission doublet.