The Effect of Photoexcitation on Formation of Radiation Defects in Si
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THE EFFECT OF PHOTOEXCITATION ON FORMATION OF RADIATION DEFECTS IN SI
V.N.MORDKOVICH, A.B.DANILIN, YU.N.EROKHIN, S.N.BOLDYREV Institute of Microelectronics Technology and High Purity Materials USSR Academy of Sciences, 142432, Chernogolovka, Moscow rgn., USSR ABSTRACT Photoexcitation of the Si electronic subsystem during ion implantation was found to be able to control radiation damage accumulation. Conditions when additional light illumination during ion bombardment suppresses radiation defect formation are determined. The model of effect observed taking into account recombination of nonequilibrium electron and holes is proposed. Coefficient between the change in amount of damage accumulated and the rate of nonequilibrium charge carriers generation is estimated.
INTRODUCTION During the last decade were published a number of papers emphasizing the fact. that photoexcitation of electronic subsystem of elementary semiconductors as well as semiconductor compounds causes significant influence on damage accumulated. It was found that light illumination may stimulate radiation defect annealing, enhance diffusion of impurity atoms, change the phase transformation temperature and control the nature of defect-impurity complexes [1-4]. The common feature of all these work is the study of photoexcitation effects on the preexisting damage. But recently we have found (5] that considerable effect of photoexcitation is observed in the case when photoexcitation accompanies the process of radiation defect formation. In [5] was shown that additional light illumination of silicon during ion bombardment may change the rate of radiation defect accumulation. It is well known that during ion implantation a number of quasichemical reactions between different types of intrinsic point defects and impurities are going on. As the result of the reactions a large variety of defect complexes is created starting from as simple as divacancy to such extended as amorphous regions (and in the extreme case continuous amorphous layers) [6]. The purpose of the present work is to find the answer on the question about the way of influence of light illumination on such a complex (and spatially nonhomogeneous) defect structure. Additional photoexcitation was carried out with irradiation of the sample face surface by the light of high pressure mercury arc lamp during ion bombardment. (100) n- and p-type silicon Mat. Res. Soc. Symp. Proc. Vol. 201. c1991 Materials Research Society
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cm 3 with charge carriers concentration from 6*1012 cm-3 to 1017 was used. Ion implantation was carried out with the use of 500 keV commercial ion implanter from High Voltage Engineering Europa B.V., the Netherlands.
RESULTS AND DISCUSSION Formation processes of different radiation defect types during ion implantation are in a good agreement with the diffusion-coagulation model. This model is based on the assumption that large complexes are formed as a result of interaction of simples defects with lower order complexes [7]. For this reason the first aim of our investigatio
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