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

A photoluminescence (PL) study of vanadium-related defects in semi-insulati ng and co-doped p-type and n-type CdTe:V crystals gives evidence of the pre sence of the V2+-Zn complex. In addition to the T-3(2)(F) --> (3)A(2)(F) em ission of V3+ near 0.5 eV and the T-4(2)(F) --> T-4(1)(F) transition of V2 near 0.45 eV, two further luminescence bands are detected at higher energi es. The first emission band (I), peaking around 0.8 eV, is correlated to th e V2+-Zn complex and the second one (II), peaking around 0,6 eV, is attribu ted to the acceptor level introduced by the cadmium vacancies. Varying the zinc concentration in CdTe, we analyse the behaviour of the vanadium impuri ty charge state. We show that the V2+ internal transition decreases with zi nc alloying due to the formation of the V2+-Zn complex. The emission bands related to isolated V-Cd 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 do minated by Emission I related to the V2+-Zn complex, The presence of this c omplex in the semi-insulating crystals used in photorefractive (PR) applica tions and the dominance of this complex over the optical properties of Cd(Z n)Te:V imply the contribution of this complex to the PR processes. (C) 2001 Elsevier Science B.V. All rights reserved.