Low-temperature photoluminescence of CdTe:Fe single crystals for tunable lasers operating in mid-infrared spectral range

We study low-temperature photoluminescence of CdTe:Fe single crystals in the near-IR range at Helium temperatures. We establish that doping with 4 · 10¹⁸ cm⁻³ iron concentration leads to a decrease of the band gap by 8 ± 1 meV compared to non-doped CdTe. We show that, in the spectral range of 1.2–1.6 eV, the luminescence of crystals is mainly defined by Hydrogen-like donors and two types of acceptors with binding energies of 149 ± 5 meV and 45 ± 2 meV. In addition, we detect the luminescence bands with maxima of 1.1 eV and 0.95 eV in the longer wavelength region. The characteristic decay time for each of the bands is 0.386 ms at 7 K. The observed bands are ascribed to intracenter luminescence corresponding to the ³T₁(³H) → ⁵E(⁵D) and ⁵T₂(⁵D) → ⁵E(⁵D) transitions between Fe²⁺-ion inner shells. Detection and identification of these bands allows the use of the near-IR range for the study of optically active iron ions in promising laser media based on CdTe:Fe.