Multiconfigurational Carbon-Group V Pair Defects in Silicon
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MULTICONFIGURATIONAL CARBON-GROUP V PAIR DEFECTS IN SILICON E. GURER and B. W. BENSON Department of physics, Lehigh University Bethlehem, Pennsylvania, 18015 Abstract*
In addition to a new configuration of the previously reported multistable carbonphosphorus pair, we report on two new multiconfigurational defects in electron irradiated silicon doped, with arsenic and antimony. These defects are also identified as interstitial carbon-substitutional group V pairs, (Ci-D.). We identified two different types of metastability for Ci-D~V. Type I is similar to the bistable carbon-carbon pair defect for which a bond switching mechanism has been reported [1]. Type II is similar to donoracceptor pairs in silicon which show electrostatically driven metastability [2,3]. The three Ci-Dv' pairs have many similar features, but also show surprising donor related differences. In this paper we will discuss the general features of these defects. Introduction
Carbon interstitial is a major irradiation product in electron irradiated silicon. Ci has a single acceptor state at E,-0.1 eV [4,5] and it migrates above 300K, forming bistable carbon-carbon pairs [1] and multistable carbon-phosphorus pairs [6,7] in phosphorus doped silicon. Recently, we discovered two new multistable defects, one in arsenic [8] and another one in antimony (91 doped, carbon rich silicon. These two defects are also observed after Ci anneals, and they anneal themselves into Ci-C 8 pairs at higher temperatures. This new finding supports the tentative identification of the multistable defect in P doped Si. We therefore identify these defects as Ci-D.V pairs, formed when migrating interstitial carbon is trapped by a substitutional group V atom. Transformations among the configurations can be induced by manipulating the charge state and the temperature of the sample. Six, five, and six energy levels have been observed for Ci-P,, Ci-As, and Ci-Sb, respectively using DLTS and TSCAP. Arranging the conditions under which various levels are observed, we identify four configurations for both Ci-As, and Ci-Sh, and five configurations for Ci-P, pairs as shown in fig. 1. The numbers in each box represent energy level positions corresponding to the particular configuration of Ci-P,, Ci-As, and Ci-Sb. pairs. The DLTS emission energies have been corrected by 2kT for the temperature dependence of electron density of states in the conduction band and the temperature dependence of the thermal velocity of electrons, except for the 0.27 eV level of IIA. None of the levels have been corrected for the temperature dependence of the electron capture cross section. Also included in fig. 1 are the energy barriers for transformations among various configurations. All of the Ci-DV pairs have a stable configuration (I) with a level around E,-0.4 eV to which the defect returns upon thermal annealing. In the case of Ci-P° we discovered a new configuration (IV) which has two energy levels at 0.07 and 0.39 eV (first and second ionization levels) after injecting minority carriers at 140K [10]. Re
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