High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties
- PDF / 178,907 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 20 Downloads / 181 Views
High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties V. Touboltsev, J. Räisänen, E. Johnson1, A. Johansen1 and L. Sarholt1 Department of Physics, University of Jyväskylä, Jyväskylä, Finland 1 Ørsted Laboratory, Niels Bohr Institute, University of Copenhagen, Denmark ABSTRACT High-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350oC and 550oC to a fluence of 1015 cm-2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation. In the samples implanted at 350oC Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600oC showed that the solid phase epitaxial regrowth of the damaged layers strongly depends on both the Ge concentration in the alloys and the temperature of annealing. Along with the recrystallization of the damaged matrix, annealing was observed to induce simultaneous removal of nearly all the implanted Er as the recrystallization front progresses towards the surface. In contrast, high temperature implantation at 550oC led to spontaneous recovery of the alloy crystallinity and incorporation of considerable fraction of implanted Er atoms on regular tetrahedral interstitial sites in the host lattice. INTRODUCTION In the past few years, optical properties of Er incorporated into semiconductors have been given a great deal of attention due to potential applications in optoelectronics [1]. Si based materials are of particular interest as luminescence from Er at a wavelength of 1.54 µm corresponds to the minimal optical absorption of silica [2]. Incorporation of Er into Si-based chips might provide the basis for integrated circuits with optoelectronic interconnections and, therefore, with considerably improved performance. However, due to the limited solid solubility of Er in Si-based materials, Si-Er structures produced so far by thermal equilibrium methods (e.g. doping during MBE growth) show insufficient emission at room temperature. The band gap energy of the host semiconductor is well known to be an important parameter for optimization of the emission [3]. In a Si1-xGex host the band gap energy and thus the energy transfer can reach acceptable levels when the Ge concentration x is changed [4]. Therefore, Si1-xGex alloys form a promising material for fabrication of advanced optoelectronic devices with low cost integrability in conventional Si technology. Since ion implantation by nature is a nonequilibrium process, it can be used to extend the concentration of optically active Er atoms in Si1-xGex alloys well beyond the terminal equilibrium solid solubility limit. Here we present results of our investigation of structural and thermal properties of Si1-xGex alloys implanted with high fluence of Er. The a
Data Loading...
