* Corresponding author. Fax: #33 4 72 43 85 31; e-mail: zerrari@insa.insa-lyon.fr. 0022-0248/99/$ — see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 8 ) 0 0 7 7 0 - 2 Journal of Crystal Growth 197 (1999) 729 — 732 Investigation of deep levels in vanadium-doped CdTe and CdZnTe A. Zerrai*, M. Dammak, G. Marrakchi, G. Bre´mond, R. Triboulet, Y. Marfaing  Laboratoire de Physique de la Matie % re, UMR CNRS 5511, INSA de Lyon, Batiment 502, 20 av. Albert Einstein, F-69621 Villeurbanne Cedex, France  Laboratoire de Physique des Solides, CNRS Bellevue, 1 place A. Briand, F-92195 Meudon, France Abstract Deep levels in vanadium-doped CdTe and CdZnTe crystals grown by vertical Bridgman for photorefractive applica- tions are reviewed. Based on photo-induced current transient spectroscopy, deep-level transient spectroscopy and deep-level optical spectroscopy, deep traps are identified and their electrical and optical properties are characterized. A discussion about their origin and a comparison with results obtained by other spectroscopy techniques are given.  1999 Elsevier Science B.V. All rights reserved. Keywords: Cadmium telluride; Vanadium; Deep-level characterization; Photorefractivity; DLTS; DLOS; Optical cross- section; Capture barrier 1. Introduction The investigation of photorefractive (PR) semiconductors is strongly motivated by near-in- frared applications in the 1—1.5 m wavelength range. CdTe doped with vanadium (V) has shown high sensitivity and attractive PR gain at 1.32 and 1.55 m [1,2] and is becoming a real promising material for applications in optical telecommunica- tion. An important parameter to characterize the photorefractive gain is the electron—hole com- petition factor  [3]. This factor depends on the photoionization cross-sections   and   of the concerned photorefractive deep level as well as on its effective concentrations n  and p  of electrons and holes, respectively. Characterization of deep traps and the understanding of their electrical and optical properties are then necessary to improve the photorefractive efficiency and to control the growth reproducibility of PR materials. The goal of this paper is to investigate the majority and minority traps detected in the band gap of vanadium-doped CdTe and CdZnTe elaborated for photorefractive applications. New experimental results are correlated to the results given in pre- vious work [4]. A special attention is carried out on