Incorporation of Highly Concentrated Iron Impurities in InP by High Temperature Ion Implantation
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,QFRUSRUDWLRQRI+LJKO\&RQFHQWUDWHG,URQ,PSXULWLHVLQ,Q3E\+LJK7HPSHUDWXUH,RQ ,PSODQWDWLRQ T. Cesca1, A. Gasparotto1, N. El Habra1, A. Coati1, B. Fraboni2, F. Priolo3, E.C. Moreira3, G. Ciatto4, and C. Bocchi5. 1 INFM and University of Padova, Physics Dept., Via F. Marzolo 8, I-35131 Padova, Italy. 2 INFM and University of Bologna, Physics Dept., V.le Berti-Pichat 6/2, I-40137 Bologna, Italy. 3 INFM and University of Catania, Physics Dept., Corso Italia 57, I-95129 Catania, Italy. 4 CNR, GILDA, ESRF, BP 220, F-38043 Grenoble Cedex, France. 5 CNR-Maspec, Parco Area delle Scienze 37/A, I-43100 Parma, Italy. $%675$&7 Iron was introduced in InP by ion implantation with the aim of obtaining a high concentration of substitutional, electrically active, deep level impurities. A substrate temperature higher than 200 °C was maintained during implantation in order to reduce damage accumulation and Fe defect reactions. The lattice position of the implanted Fe atoms and its modification during annealing treatments was studied by means of Proton Induced X-ray Emission (PIXE) in channeling conditions and correlated with the ion induced damage measured by different techniques. The results show that a high fraction of substitutional Fe atoms is present after the implantation. This fraction is progressively reduced during thermal treatments by increasing the annealing temperature, with the formation of inactive Fe aggregates, probably in the form of small Fe-P complexes. ,1752'8&7,21 Among other impurities in InP Fe plays a special and important role. Thanks to its midgap deep acceptor character, Fe doping is employed to produce bulk and epitaxial semi-insulating InP and is widely used in the optoelectronic device technology; furthermore, intracenter d-shell transitions between Fe2+ states could be exploited to produce a light emitter in the mid-IR region [1,2]. In order to display these properties, due to their chemical nature, Fe atoms have to be substitutionally located in a regular lattice. A major drawback is the rather low Fe solubility, which limits the active iron concentration achievable with equilibrium techniques to values 1x1017 cm-3. Ion implantation could in principle be used to overcome solubility limitations, but the strong reactivity of iron with the implant induced crystal defects and the difficulty of reconstructing highly damaged InP crystals pose severe questions to its use, especially for high implantation doses . In our approach we heated the substrate at a temperature T &GXULQJWKH implantation. The dynamical annealing effects associated with the elevated temperature allow both to strongly reduce the damage production and to minimize Fe-defect reactions. With this method local electrical compensation and semi-insulating layer formation in substrates with ndoping up to 1x1019 cm-3 has been obtained [3,4]. In this work we present a detailed investigation of the implant induced crystal modifications, with special attention paid to the local structure around the Fe implanted atoms; our goal is
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