Metal-nonmetal transition and resistivity of silicon implanted with bismuth
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Metal-nonmetal transition and resistivity of silicon implanted with bismuth E. Abramof and A. Ferreira da Silva Instituto Nacional de Pesquisas Espaciais (INPE), Laborat´orio Associado de Sensores e Materiais-LAS, CP 515, 12201-970 S˜ao Jos´e dos Campos-SP, Brazil
Bo E. Sernelius Department of Physics, Link¨oping University, S-581 83 Link¨oping, Sweden
J. P. de Souza and H. Boudinov Instituto de F´ısica – UFRGS, 91501-970 Porto Alegre-RS, Brazil (Received 11 March 1996; accepted 24 October 1996)
Bismuth was implanted at room temperature in (100)-Si wafers with controlled energy and doses to result in a plateau-like implantation profile. The van der Pauw Si : Bi samples were characterized by the Hall effect and resistivity measurements from room temperature down to 13 K. The electron concentration of the prepared samples at 290 K varied from 3.0 3 1017 to 1.4 3 1020 cm–3 . The resistivity of the Si : Bi samples presents a larger enhancement, compared to other dopants, when decreasing the Bi concentration. The metal-nonmetal transition was determined to be around 2 3 1019 cm–3 . The calculated values obtained from the Generalized Drude Approach and an equation derived from Kubo formalism agree very well with the experimental data. The results confirm also the behavior rc sBid , rc sAsd , rc sPd , rc sSbd at 290 K.
I. INTRODUCTION
II. EXPERIMENTAL
The ion implantation is an essential process for the fabrication of electronic devices and integrated circuits.1 The investigation of the electronic properties of doped semiconductors continues to be of considerable interest mainly because these materials appear as good model systems for the study of combined effects, such as disorder and electron correlation, as well as in the analysis of critical exponent at the metal-nonmetal (MNM) transition.2–5 Silicon doped with bismuth is an interesting choice because the ionization energy of Bi in Si is much larger than that of other group-V elements (P, As, and Sb). In this case, the theory of effective mass is expected to be less applicable.2,3 Besides that, Bi has been observed to have a low equilibrium solid solubility in silicon crystal.6 However, a previous investigation of the annealing behavior of Bi implanted into Si during rapid thermal annealing evidenced that metastable concentration of electrically activated Bi well above the solid solubility limit can be obtained.7 In this work we present a detailed study of the electrical properties of silicon implanted with bismuth. Resistivity and Hall effect measurements were performed in Si : Bi samples from room temperature down to 13 K with donor impurity concentration in the range of 3.0 3 1017 to 1.4 3 1020 cm–3 . The experimental results were compared with the ones calculated from the Generalized Drude Approach and an equation derived from the Kubo formalism.
The Si wafers used were of p-type and (100) oriented with resistivity in the range of 16 to 25 V ? cm. Before bismuth implantation, small Si chips (6 3 6 mm2 ) were prep
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