Defect-Formation Dependence on Group V-Dopant Atoms in Electron-Irradiated Silicon
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DEFECT-FORMATION DEPENDENCE ON GROUP V-DOPANT ATOMS IN ELECTRON-IRRADIATED SILICON 0.0. AWADELKARIM*, A. HENRY*, B. MONEMAR* AND J.L. LINDSTROM** * Department of Physics and Measurement Technology, Link6ping University, S-581 83 Link6ping, SWEDEN "**National Defence Research Establishment, P.O. Box 1165, S-581 11 Linkdping, SWEDEN ABSTRACT The defect states introduced in P-, As- and Sb-doped silicbn upon roomtemperature electron-irradiation are studied by deep-level transient spectroscopy (DLTS). Evidence is provided for the involvement of the P-atom and the vacancy in the defect complex giving rise to the prominent electron trap commonly observed at = EC-0.4 eV (EC being the edge of the conduction band). This electron trap together with another at EC-0.30 eV, apparently phosphorus related, exhibit configurationally metastable behaviour. Other electron traps observed at EC-0.27 eV and EC-0.51 eV in Sb-doped material and EC-0.34 eV in As-doped material are attributed to complexes involving Sb and As atoms, respectively. INTRODUCTION Irradiated silicon crystals are expected to contain vacancies (V) and self interstitials (Sii). However, complexes of intrinsic defects and impurity atoms can also be formed rendering the system more complicated. In irradiated n-type material complexes comprising column V donors (P, As, Sb, Bi) have been a subject of intensive studies [1-4]. Among such complexes P-V (E centre), As-V and Sb-V centres were observed by electron paramagnetic resonance (EPR) [1,2]. From DLTS studies the E-centre has been assigned an electron trap observed at EC-0.4 eV [4]. However, as more DLTS data became available this assignment has become progressively weaker. Several other defects, some of which are configurationally multistable, are reported to have electron traps at EC-0.4 eV [5,6]. Notably, these traps anneal out at temperatures below 200 'C where the E-centre is known to disappear [1]. In this study we investigate the role of group V impurities, namely P, As and Sb atoms, in the defect formation and stability in irradiated n-type silicon. EXPERIMENTAL PROCEDURE The samples used in this study were n-type P-, As- and Sb-doped silicon cut from float-zone (FZ) and Czochralski (Cz) single crystals. The dopant concentrations were in the range =1014-1016 cm- 3 . The samples were irradiated by 2.0 MeV electrons at room temperature to a total dose of 1.0x10 16 e-/cm 2 . Heat treatments on the samples were performed at 100, 200 and 300 °C for durations of 60 minutes. Schottky barrier structures on the samples were prepared by gold evaporation at a pressure of =l.0xl0-8 Torr. The DLTS measurements were carried out using a standard experimental setup [7]. The configurational stability of the traps is observed by cooling down the diodes from room temperature to liquid nitrogen temperature under zero- or reversebias conditions, as discussed by Benton and Levinson [8].
Mat. Res. Soc. Symp. Proc. Vol. 163. ' 1990 Materials Research Society
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EXPERIMENTAL RESULTS
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