Specific features of the effect of irradiation with electrons and neutrons on photoelectric properties of CdS single cry
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ICATION, TREATMENT, AND TESTING OF MATERIALS AND STRUCTURES
Specific Features of the Effect of Irradiation with Electrons and Neutrons on Photoelectric Properties of CdS Single Crystals Nominally Undoped and Doped with Cu H. Ye. Davidyuk, V. V. Bozhko, and L. V. Bulatetska^ Lesya Ukrainka Volyn National University, Lutsk, 43025 Ukraine ^e-mail: [email protected] Submitted January 14, 2008; accepted for publication February 4, 2008
Abstract—Electrical, photoelectric, and magnetic properties of CdS single crystals undoped and doped with copper (NCu ≈ 1018 cm–3) and irradiated with electrons (E = 1.2 MeV, Φ = 2 × 1017 cm–2) and neutrons (E = 2 MeV, Φ = 1018 cm–2) are studied. It is shown that the donor–acceptor pairs are responsible for extrinsic pho– toconductivity and paramagnetic properties; in particular, these pairs are represented by Cu Cd –D+ complexes that are destroyed during irradiation and are formed again with time (as secondary radiation defects) in irradiated samples. It is established that the majority of paramagnetic centers and donor–acceptor pairs are located in the near-surface region of the crystal. It is confirmed that large structural defects (defect clusters) formed by irradiation with neutrons are efficient sinks for copper atoms. Specific features of isochronous annealing of paramagnetic centers and donor–acceptor pairs responsible for the variation in magnetic parameters and in the photoconductivity spectra of irradiated undoped and Cu-doped CdS samples are studied. PACS numbers: 78.55.Et, 73.50.Pz, 61.80.-x, 61.82.Fk, 81.40.Wx DOI: 10.1134/S1063782608100187
1. INTRODUCTION In the current state of development of nuclear power engineering and cosmic technologies, one of the important problems to be solved in the production of semiconductor devices consists in fabrication of radiationresistant and photosensitive materials for electronics and optoelectronics. Promising materials with the above properties include certain semiconductor compounds, in particular, CdS single crystals. This study is a continuation of that published previously [1] and is concerned with gaining insight into the effect of irradiation with electrons on photoelectric properties of undoped and Cu-doped CdS single crystals. It is known [2–4] that many of the primary radiation defects in the II–VI semiconductors are mobile at room temperature. In addition, these defects become involved in quasi-chemical reactions with various uncontrolled impurities present in the crystal and form complexes responsible for variation in various parameters of semiconductors. In this context, special attention in this study is given to the purity of the original material and to the use of high integrated doses of radiation at which the concentration of radiation defects would be easily higher than the concentration of uncontrolled impurities. The choice of copper as doping impurity in CdS single crystals is motivated by the important role of this
impurity in formation of various optically active centers in the II–VI semiconductors. The CdS single cr
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