Optical Methods for Defect Characterization in Light-Ion Implanted Silicon Carbide
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Optical Methods for Defect Characterization in Light-Ion Implanted Silicon Carbide Claudiu I. Muntele, Iulia C. Muntele, Daryush Ila Center for Irradiation of Materials, Alabama A&M University, P. O. Box 1447, Normal, AL – 35762, U. S. A., Phone 1-256-851-5866, Fax 1-256-851-5868, Email [email protected] David B. Poker, Dale K. Hensley Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN, U. S. A.
ABSTRACT The work reported here deals with studying the defects induced by light ion (Al, N) implantation in 4H and 6H silicon carbide, both p-type (Al-doped) and n-type (N-doped). Confocal Micro-Raman (MR) was used for monitoring the (480 – 540) cm-1 spectral region of amorphous silicon. A broad peak forms in this region because of silicon atoms relocated as interstitials, translating into a locally stressed crystalline lattice. The locally relaxed lattice at these atoms’ locations of origin also gives a broadening of the characteristic Raman peaks of each type of material. UV/Vis Optical Absorption (OA) Spectroscopy has also been employed as a good tool for dopant and carrier trapping levels embedded in the band gap of the silicon carbide material. MR and OA data collected from virgin samples, as implanted, and after annealing at two different temperatures (1100 and 1600 °C) are discussed in this paper. INTRODUCTION Silicon carbide is one of the materials of choice for hydrogen sensors’ fabrication. Its ability to function at elevated temperatures (up to 800 °C) in an oxidizing environment, with only a minor rise in the noise current, makes it interesting for applications in harsh conditions, completely unsuitable for any other known semiconductor materials. One approach in fabricating stable, reliable hydrogen sensors is ion implantation, followed by ion milling for removing the damaged surface layer. Our present studies of silicon carbide focus on following the damage due to implantation, its evolution at elevated temperatures, and the stability of the sensor over time with respect to the native imperfections and additionally induced damages. In order to identify the influence of doping elements to the silicon carbide base material, we chose to implant additional aluminum into Al-doped silicon carbide, and nitrogen into N-doped silicon carbide, and monitor the evolution of the implantation damage (amorphization, vacancies, interstitials, cluster formation) induced. For the present case we chose 6H p-type, and 6H and 4H n-type silicon carbide. The samples were heavily implanted with aluminum and nitrogen respectively, annealed and analyzed using MR and OA spectroscopic tools.
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EXPERIMENTAL WORK Samples of p-type and n-type (N-doped) silicon carbide were implanted with aluminum and nitrogen at 2 MeV with fluences of 1017 ions/cm2 at 600 °C (Table I). The ion im
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