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FORMATION OF STABLE POINT DEFECTS IN ION-IMPLANTED Si* R.J. CULBERTSON AND S.J. PENNYCOOK Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 ABSTRACT Double doping of Si by ion implantation of both group V and group III dopants was studied. For the case of Sb as the group V dopant, both Sb and B could be maintained in solution after high temperature heat treatment at concentrations greatly exceeding their solubility limits. With Sb implantation alone, Sb diffusion takes place with a highly enhanced transient diffusion, followed by nucleation of self interstitials into loops at the projected range. In certain double-doped samples this projected range damage was eliminated. In the under-compensated B-Sb case, evidence of stable Sb-B pairs was obtained. INTRODUCTION Supersaturated semiconductor alloys formed by moderate annealing of Si implanted with a high fluence of a group V dopant, such as Sb, Bi, or P, display a highly enhanced diffusion transient during subsequent annealing. The diffusion coefficients are determined from the annealing time and the size distribution of precipitates. This transient ends with the formation of self-interstitial loops at the projected range. The case of As also ends with the band of interstitial loops, although As precipitates are not seen [1]. These phenomena have been explained by Si interstitials trapped by the dopant atoms during the implantation process. The resulting defect complex is sufficiently stable to survive solid-phase epitaxial (SPE) growth, which typically involves heating to 600°C for 60 min. Further annealing at higher temperatures or longer times dissolves these complexes, and the release of the self-interstitials results in highly enhanced diffusion of the dopant atoms via an interstitialcy mechanism. The interstitials soon condense into the observed loops at the projected range. Similar effects for group III dopants are not seen. A model to explain the stability of the group V-Si complexes and the lower stability of group Ill-Si complexes was proposed [1]. Double doping experiments [2] have shown that the above phenomena are strongly affected by following or preceding the implantation of the group V species with the implantation of a group III species. For the undercompensated case, i.e., implanted the group III species (B) to a concentration comparable to or less than the group V dopant (Sb or As), results in the suppression of the projected range damage and an improvement of the substitutionality of the group V dopant. For the over compensated case the transient-enhanced diffusion of the group V dopant (Sb) was also suppressed, and no transient-enhanced B diffusion was observed. Recent experiments using the perturbed-angular-correlation (PAC) technique have provided direct evidence for the formation of In-As pairs and complexes [3] and In-P and In-Sb pairs [4]. B-Sb pairing has been proposed to explain retarded Sb diffusion in B-doped Si [5]. In the present work, ion channeling results give direct evidence for pairing in the B-Sb case. Als