Electrical properties and photoluminescence of SiO x layers with Si nanocrystals in relation to the SiO x composition
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Electrical Properties and Photoluminescence of SiOx Layers with Si Nanocrystals in Relation to the SiOx Composition I. V. Antonovaa^, M. B. Gulyaeva, Z. Sh. Yanovitskayaa, V. A. Volodina, D. V. Marina, M. D. Efremova, Y. Goldsteinb, and J. Jedrzejewskib aInstitute
of Semiconductor Physics, Siberian Division, Russian Academy of Sciences, ul. Institutskaya 4/1, Novosibirsk, 630090 Russia ^e-mail: [email protected] bRacah Institute of Physics, Hebrew University, Satra, Givant Ram, 91904 Jerusalem, Israel Submitted February 13, 2006; accepted for publication February 27, 2006
Abstract—The photoluminescence and electrical properties are compared for silicon-oxide layers containing Si nanocrystals and having different Si content. The oxide was deposited by co-sputtering of silicon dioxide and silicon with the subsequent annealing for the formation of nanocrystals. Excess Si content in the layer varies along the sample from 6 to 74 vol %. It is found that a charge magnitude determined from the flat-band voltage has a pronounced peak for the excess Si content of about 26%, the largest charge correlating with the highest photoluminescence intensity. The further increase in the excess Si content in oxide leads to a decrease in both the oxide charge and the photoluminescence intensity and to the appearance of percolation conductivity. PACS numbers: 81.15.Cd, 78.67.Bf, 61.46.Bc, 73.63.Bd DOI: 10.1134/S1063782606100137
1. INTRODUCTION The fabrication of dielectric layers containing an ensemble of semiconductor nanocrystals (Si, Ge, etc.) is a promising trend in the development of siliconbased optoelectronic devices [1, 2]. The first LEDs based on silicon [1] have already appeared. Such layers are also of interest due to the possibility of fabricating devices operating on the principle of quantum-size effects at a relatively high temperature [3]. In addition, the use of photons instead of electrons for the information transfer in circuits is suggested as a promising solution to problems of nanosize electronics [4]. The most known and actively developed methods for obtaining nanocrystals in a SiO2 layer are Si and Ge ion implantation [5], plasma deposition [6], and cosputtering of silicon dioxide and silicon [7]. The hightemperature thermal treatment of the layers fabricated by all these methods leads to the formation of Si nanocrystals (nc-Si) in the SiO2 matrix and to the appearance of photoluminescence (PL).
charge precede the appearance of the percolation conductivity through the dielectric layer. 2. EXPERIMENTAL As an original substrate, we used an n-Si (100) wafer with an initial electron concentration of 2.5 × 1015 cm–3. The sample length was 14 cm. On its surface, we fabricated a SiO2 oxide layer with an excess Si content variable along the sample. For the fabrication of this layer, we used the co-sputtering of SiO2 and Si targets arranged at a distance of 100 mm from each other in argon plasma. Figure 1 illustrates the layout of the co-sputtering. The substrate was not specially heated during the
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