Growth of Si 1-x .Sn x Layers on Si by Ion-Beam-Induced Epitaxial Crystallization (Ibiec) and Solid Phase Epitaxial Grow
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Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305 Japan Meiji University, 1-1-1 Higashimita, Tama, Kawasaki, Kanagawa 214, Japan
ABSTRACT Synthesis of metastable group-IV binary alloy semiconductor thin films on Si was achieved by the crystalline growth of Sil-,Sn, layers using Sn ion implantation into Si(100) followed either by ion-beam-induced epitaxial crystallization (IBIEC) or solid phase epitaxial growth (SPEG). Si(100) wafers were implanted at room temperature with ll0keV 120 Sn ions to a dose of 1x1016 cm-2 (x=0.029 at peak concentration) and 2x1016 cm- 2 (x=0.058 at peak concentration). By this process about 90nm-thick amorphous Silx-,Snx and about 30nm-thick deeper amorphous Si layers were formed. IBIEC experiments performed with 400keV Ar ions at 300-400'C have induced an epitaxial crystallization of the amorphous alloy layers up to the surface and lattice site occupation of Sn atoms for samples with the lower Sn concentration (LC). XRD analyses have revealed a partial strain compensation for the crystallized layer. Samples with the higher Sn concentration (HC) have shown an epitaxial crystallization accompanied by defects around the peak Sn concentration. SPEG experiments up to 750'C for LC samples have shown an epitaxial crystallization of the fully strained alloy layer, whereas those for HC samples up to 750'C have revealed a collapse of the epitaxial growth around the interface of the alloy layer and the Si substrate. Photoluminescence (PL) emission from both IBIEC-grown and SPEG-grown samples with the lower Sn concentration has shown similar peaks to those by ion-implanted and annealed Si samples with intense I1 or I 1-related (Ar) peaks. Present results suggest that IBIEC has a feature for the non-thermal equilibrium fabrication of Si-Sn alloy semiconductors. INTRODUCTION Feasible attractive physical properties due to the bandgap engineering and the structural modification in group-IV alloy semiconductors based on Si are of interest from the electronic and photonic engineering point of view [1, 2]. SiGe and SiGeC are typical examples showing structural and electronic characteristics of interest [2-4]. Here we direct our attention to a binary alloy of Si-Sn, because cc-Sn is a zero-bandgap semiconductor and Si 1-xSnx can produce smaller bandgap semiconductors. Nevertheless, Sn atoms are difficult to incorporate in Si due to their low solid solubility (less than 0.1 at.% at 1066-C for Sn in Si) [5]. Ion implantation is a technique suitable for the introduction of foreign atoms and has the advantage of being compatible with present Si technology. Subsequent solid phase epitaxial growth (SPEG), however, is known to fail in epitaxial Sia.,Sn,, layer growth (for x>0.0 2 ) due to an amorphousto-polycrystalline phase transformation [6]. On the other hand, ion-beam-induced epitaxial crystallization (IBIEC) is known to incorporate foreign atoms at concentrations far in excess of their solubility limit at lower temperatures than those required for SPEG process, which is demonstrated for Si r-x
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