Photoluminescence and absorption identification of Ti³⁺ in zinc telluride

Low-temperature photoluminescence (PL) and optical absorption are carried out on a Ti-doped ZnTe bulk crystal with carefully optimized experimental conditions. The influence of excitation energy in the PL is checked. Two zero-phonon lines (ZPLs) are clearly identified and phonon sidebands are evidenced in the PL and in the absorption, respectively. A relation is established between the PL and the absorption for the intensity ratio of the two ZPLs. Thereby, the Ti ion is identified as Ti³⁺ and the ZPLs in the PL spectrum are from the Γ₇ and Γ₈ levels of the ²T₂ excited state to the well-separated Γ₈ level of the ²E ground state. The separation of the two excited levels is 2.4 cm^-1. The population numbers are shown to be fully thermalized in the ²T₂ excited state in the PL process.