A photoluminescence study of vanadium-related defects in n-type, semi-insulating and p-type Cd(Zn)Te

Abstract A photoluminescence (PL) study of vanadium-related defects in semi-insulating and co-doped p-type and n-type CdTe:V crystals gives evidence of the presence of the V2+–Zn complex. In addition to the 3 T 2 ( F )→ 3 A 2 ( F ) emission of V3+ near 0.5 eV and the 4 T 2 ( F )→ 4 T 1 ( F ) transition of V2+ near 0.45 eV, two further luminescence bands are detected at higher energies. The first emission band (I), peaking around 0.8 eV, is correlated to the V2+–Zn complex and the second one (II), peaking around 0.6 eV, is attributed to the acceptor level introduced by the cadmium vacancies. Varying the zinc concentration in CdTe, we analyse the behaviour of the vanadium impurity charge state. We show that the V2+ internal transition decreases with zinc alloying due to the formation of the V2+–Zn complex. The emission bands related to isolated VCd are present with high intensity only in the p-type crystals, in which all the vanadium content is in the V3+ oxidation state, whereas, in the semi-insulating and n-type crystals, the PL spectrum is dominated by Emission I related to the V2+–Zn complex. The presence of this complex in the semi-insulating crystals used in photorefractive (PR) applications and the dominance of this complex over the optical properties of Cd(Zn)Te:V imply the contribution of this complex to the PR processes.