An Electron Paramagnetic Resonance Investigation of Iron-Indium Pairs in Silicon
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AN ELECTRON PARAMAGNETIC RESONANCE INVESTIGATION OF IRON-INDIUM PAIRS IN SILICON P.
EMANUELSSON*, W. GEHLHOFF**, P. OMLING* AND H. G. GRIMMEISS* *Department of Solid State Physics, University of Lund, Box 118, S-221 00 Lund, Sweden **Academy of Sciences of the GDR, Centre for Scientific Instruments, Rudower Chaussee 6, Berlin 1199, GDR ABSTRACT Three different Electron Paramagnetic Resonance (EPR) signals, one trigonal and two orthorhombic, which originates from iron-indium pairs in silicon are investigated. It is shown that the two orthorhombic spectra can be explained as transitions within the two doublets of a S=3/2 system with a large zero-field splitting. The temperature dependence of the intensities reveals that the newly discovered spectrum corresponds to the lower doublet and that the zero-field splitting is 9.8 ± 2.0 cm-1 . INTRODUCTION Pairs of a substitutional group III acceptor and an interstitial iron atom in silicon have been extensively studied in recent years [1-7), partly due to the fact that these defects can exist in two different configurations [1]. The two structural arrangements are the nearest neighbour configuration (nn) where the interstitial iron atom is situated along a direction from the acceptor (trigonal symmetry) and the next nearest neighbour configuration (nnn) where the iron atom is situated along a direction (orthorhombic I symmetry). The Electron Paramagnetic Resonance (EPR) investigations of iron-acceptor pairs [2-4] have revealed that the FeAl and FeGa centres exist in both the nn and the nnn configuration. For the orthorhombic pairs an additional spectrum, belonging to an excited state, has been detected. FeB is only found in the nn configuration and FeIn in the nnn. The spectra can be described as transitions within the two doublets of a S=3/2 system with a large zero-field splitting. The ground state spectrum then corresponds to transitions within the lower doublet and the excited state spectrum to transitions within the upper doublet. The sign of the axial fine structure parameter is found positive for FeB, negative for FeAl and FeGa and positive for FeIn. This surprising chemical trend and the missing trigonal FeIn pair is an unsolved problem. However, recently a new spectrum was found that could be identified as an FeIn pair with trigonal symmetry [5). Later a new orthorhombic spectrum was detected in addition to the old orthorhombic FeIn signal [6]. It was concluded that the new spectrum belongs to the ground state and that the previously reported one corresponds to the excited state. The aim of this paper is to summarise these new findings and to present new measurements of the temperature dependencies of the two orthorhombic EPR spectra EXPERIMENTAL DETAILS The samples were prepared from Czochralski grown silicon Mat. Res. Soc. Symp. Proc. Vol. 163. ©1990 Materials Research Society
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crystals doped with indium (2 acm). Iron was evaporated onto the 57 Fe isotope samples and diffused at 1200 *C for two hours. The 57 Fe was doping took place in a closed ampoule wher
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