Photoluminescence at 1540 nm from erbium-doped amorphous silicon carbide films
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Ei Ei Nyein and Uwe Hommerich Department of Physics, Hampton University, Hampton, Virginia 23668
Alain E. Kaloyerosa) School of NanoSciences and NanoEngineering, The University at Albany-SUNY, Albany, New York 12203 (Received 17 February 2004; accepted 30 April 2004)
Room-temperature photoluminescence (PL) was observed at 1540 nm in erbium-implanted amorphous silicon carbide (a-SiC:Er) films grown by thermal chemical vapor deposition at 800 °C. The PL spectra of the a-SiC:Er samples did not exhibit any defect-generated luminescence, with the PL intensity at 1540 nm dropping only by a factor of 3.6 as the sample temperature was increased from 14 K to room temperature. Time-resolved PL measurements showed that the Er3+ luminescence lifetime of approximately 0.6 ms was nearly independent of sample temperature. In addition, luminescence quenching was observed as implanted Er dose exceeded 7 × 1015 ions/cm2. It is suggested that the lower density of Si and C vacancies in the stoichiometric a-SiC:Er, as compared to its non-stoichiometric a-Si1−xCx counterpart, along with the incorporation of a higher Er dopant concentration, can effectively quench defect-produced luminescence and lead to a significant improvement in PL performance. These properties indicate that stoichiometric a-SiC is potentially a viable candidate for optoelectronic devices operating in the 1540 nm region.
I. INTRODUCTION
Rare-earth doped materials are of great interest for a wide range of optoelectronics applications.1,2 In particular, erbium (Er) doped material systems have received significant attention, since the intra-4f electronic transition (4I13/2–4I15/2) of trivalently bonded Er3+ produces light emission at 1540 nm, a wavelength falling in the window of minimal absorption for silica optical fibers used in optical communications. Due to the extremely long lifetime of the 4I13/2–4I15/2 transition, and the shielding of 4f orbital of Er3+ by the 5s and 5p shells, Er luminescence tends to be quite sharp and virtually independent of the host material. However, the rapid reduction in luminescence intensity with increased temperature has been a key limiting factor in the development of viable optoelectronic devices based on Er-doped Si. This temperature quenching phenomenon is mainly caused by the so-called “energy back-transfer” process, in which the de-excitation of Er ions to the ground state proceeds a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0292 J. Mater. Res., Vol. 19, No. 8, Aug 2004
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nonradiatively through an Er related defect level in the band gap of Si.1,2 Attempts at Er doping of various semiconductor materials other than Si have shown that temperature quenching of Er luminescence is diminished with higher semiconductor band gaps.3–5 In particular, silicon carbide (SiC), due to its wide band gap and excellent mechanical, chemical, and physical properties, has emerged as a promising base material for use in advanced ele
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