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 <middle dot> 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.