Defect physics of the CuInSe 2 chalcopyrite semiconductor C. Rinco´n * , R. Ma´rquez Centro de Estudios de Semiconductores, Departamento de Fı ´sica, Facultad de Ciencias, Universidad de Los Andes, Me´rida 5101, Venezuela Received 22 December 1998; accepted 19 March 1999 Abstract The activation energies of acceptor E A and donor levels E D in the chalcopyrite compound CuInSe 2 are calculated by using a simpler model based in the effective-mass theory for the case of single, double and triple point defect centers. Despite of the simplicity of this model, it is found that the values of E A and E D thus calculated for shallow and deep levels are in reasonable agreement with those reported from the experimental data. In the case of not shallow donor levels values of E D in good agreement with these data are calculated by using the free electron mass m 0 instead of the effective electron mass. From the analysis of the results, most of these levels have been identified as due to the presence of several native point defects. q 1999 Elsevier Science Ltd. All rights reserved. Keywords: A. Semiconductors; A. Electronic materials; A. Optical materials; D. Electronic structure; D. Defects 1. Introduction The chalcopyrite semiconductor CuInSe 2 has emerged as a leading material for photovoltaic applications [1,2]. This is mainly because this compound can be prepared as either p- or n-type conducting by adjusting its stoichiometry. It also presents a high absorption coefficient with an appropriate band gap [1]. In fact, devices based on CuInSe 2 have demon- strated efficiencies above 16% [2,3]. However, deviation from the ideal stoichiometry originates several donor and acceptor levels which affect its electro-optical properties[4]. Although the physics of these defect levels has been studied by several techniques including optical absorption [5–9], luminescence [7,10–34], photoconductivity [12,20,35], deep-level transient spectroscopy [33,36–45], photoacous- tic spectroscopy [46–48], and electrical measurements [34,49–62], controversy still exists relating to the nature and origin of the native defect centers observed in this compound. This is because the identification of these centers has been made mainly by considering the stoichiometry of the samples studied, derived from their chemical analysis, and by calculations of the formation energies of these defects [63,64] by using models developed for the elemental and binary semiconductors. No theoretical predictions of the activation energy of these levels, except for that obtained from the hydrogenic model [14], had been reported in the literature. However, recently Zhang et al. [65,66] from the first-principles self-consistent electronic structure theory, calculated the formation energies and energy levels of several point defects and defect pairs in CuInSe 2 . Their results, although in good agreement with the activation ener- gies of the majority of deep defect levels observed in CuInSe 2 , only predict a shallow acceptor level located around 0.03 eV above the valence band maxima (BVM). This contradict most of the experimental results obtained by electrical, optical and other measurements, including recent atomic-scale image and nanoescale characterization techniques [67], which indicate that several shallow levels (E i , 0.1 eV, where E i is the activation energy of the defect level) dominate the electro-optical properties of both p- and n-type samples of CuInSe 2 . Further, their results related to the formation energies of native defects, suggesting that copper vacancies are the dominant defect centers in CuInSe 2 , also differ from that obtained recently by Sobolev et al. [68] based on the cluster calculations by the scattered wave method, and earlier by Neumann et al. [63,64] indicat- ing that antisite cation defects are the dominant centers in this material. Journal of Physics and Chemistry of Solids 60 (1999) 1865–1873 0022-3697/99/$ - see front matter q 1999 Elsevier Science Ltd. All rights reserved. PII: S0022-3697(99)00190-0 * Corresponding author. Apartado de Correos No. 1, CES, La Hechicera, Merida 5101, Venezuela. E-mail address: crincon@ciens.ula.ve (C. Rinco´n)