Micro-and nano-structures in silicon studied by DLTS and scanning probe methods
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icro- and Nano-Structures in Silicon Studied by DLTS and Scanning Probe Methods1 D. Cavalcolia, A. Cavallinia, M. Rossia, and S. Pizzinib a
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Physics Department, University of Bologna, Viale Berti Pichat 6/ll, Bologna, Italy Material Science Department, University of Milan–Bicocca, Via Cozzi 53, Milano, Italy e-mail: [email protected] Submitted September 12, 2006; accepted for publication October 3, 2006
Abstract—Presently, there is a high interest in silicon-based optical devices that would render possible the development of fully silicon-based optoelectronics. Being an indirect-gap semiconductor, silicon is poorly efficient as a light emitter since radiative emission is limited by carrier recombination at non-radiative centers. One of the possible approaches to enhance the radiative emission from Si is the controlled introduction of micro(dislocations) or nano- (nanocrystals) structures, which, providing quantum confinement of free carriers, prevent their diffusion towards non-radiative channels. Dislocations introduced in silicon by plastic deformation and Si nanocrystals embedded in the amorphous silicon matrix have been investigated by junction spectroscopy and scanning probe microscopy methods. PACS numbers: 61.72.-y, 71.55.Jv, 73.20.Hb, 73.50.Pz DOI: 10.1134/S1063782607040112
1.1 INTRODUCTION Light emission from Si is strongly inefficient, as band-to-band optical transitions are highly improbable and most of the excited electron-hole pairs recombine non-radiatively. Nevertheless, there is a strong demand for an optical emitter to be compatible with standard silicon-based ultra-large-scale integration technology. For this reason, since 1990, many strategies, reviewed in [1], have been employed to overcome these materials limitations and to obtain efficient light emission from Si. One of the most successful is based on the modification of free carrier properties by quantum confinement effects, firstly obtained by the use of porous Si [2], then by the controlled production of Si nanocrystals in a SiO2 matrix [3]. Promising results could also be expected by using nanocrystalline hydrogenated Si as it mimics a dispersion of Si dots in a matrix of a-Si characterized by a larger energy gap, and then potentially inducing quantum confinement effects, provided one succeeds in reducing the size of the crystallites to a few nm in diameter [4]. Another approach is based on the suppression of non-radiative recombination centers using for the device fabrication high quality substrates and defect passivation procedures [5]. Among the various attempts very recently made in order to increase the efficiency of radiative transitions, a significant result was obtained by defect engineering procedures, i.e., by employing dislocations as light emission sources [6]. It was, in fact, demonstrated that using an appropriate impurity gettering process followed by the dislocation 1 The
text was submitted by the authors in English.
passivation, one could achieve a large enhancement of the radiative transitions with respect to the
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