Erbium Doping of Silicon and Silicon Carbide Using Ion Beam Induced Epitaxial Crystallization
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P. Boucaud*, F.-H. Julien*, J.-M. Lourtioz*, H. Bernas**, C. Clerc**, J. Chaumont**, S. Bodnar***, J.-L. Regolini***, X. W. Lin**** IEF, Universit6 Paris XI, Bat 220, 91405 Orsay, FRANCE CSNSM, Universite Paris XI, Bat 108, 91405 Orsay, FRANCE *** France Telecom CNET-CNS, 38243 Meylan, FRANCE ****Lawrence Berkeley Laboratory, Berkeley, CA *
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ABSTRACT
Erbium doping of silicon and silicon carbide using implantation followed by ion beam induced epitaxial crystallization (IBIEC) is investigated. The implanted concentration of Er was 1.4 at% in both cases. In Si(100), Rutherford backscattering/channeling revealed that about 40% of the Er atoms evolved upon rapid thermal annealing from an undetermined position (room temperature) to an interstitial tetrahedral position (650'C) and finally to a substitutional position (950'C). The remaining Er atoms were presumably trapped in the small precipitates visible in high resolution transmission electron microscopy. The photoluminescence at 1.54 gm of ErP3 is enhanced with annealing and persists up to room temperature after a 950 'C 1 min anneal. The high concentration of optically active Er atoms is illustrated by the lack of saturation of the photoluminescence at high pumping excitation intensity. Erbium was also implanted into cubic silicon carbide films prepared by chemical vapor deposition on Si at 900 *C. Both solid phase epitaxy (SPE) and IBIEC were performed. After a 950'C anneal, the low temperature photoluminescence at 1.54 gm after IBIEC was five times higher in SiC than in silicon. The difference in photoluminescence linewidth between IBIEC (broad lines) and SPE (sharp lines) is explained in terms of interactions between optically active erbium atoms.
INTRODUCTION
The incorporation of rare earth atoms in semiconductor hosts has raised interest since the first demonstration of Er 3+ optical emission at 1.54 gm 1. The latter involves intra 4f shell transitions (4113/2-_4415/2), and is particularly well adapted to optical fiber telecommunication systems. This has led to the search for silicon-based materials in which a light emitting diode at 1.54 jm can be coupled to standard signal processing. However, two main difficulties have been raised, which limit the optical efficiency of 141
Mat. Res. Soc. Symp. Proc. Vol. 354 01995 Materials Research Society
erbium-doped silicon 2. The first limitation is the low equilibrium solid solubility of Er in silicon (_ 1018 cm- 3) which reduces the number of optically active centers. The second limitation is the temperature quenching of optical emission, which prevents room temperature operation. Oxygen co-doping and solid phase epitaxy (SPE) have recently been shown to overcome this problem, allowing room temperature operation of electroluminescence diodes 3. Instead of using SPE, we have studied the effect of ion beam induced epitaxial crystallization (IBIEC) of the Er-implanted amorphous layer. The optical properties were investigated by photoluminescence (PL), the location of Er atoms in the silicon lattice was determined
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