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4H-SiC P+N UV Photodiodes : A Comparison between Beam and Plasma Doping Processes

Abstract : This paper presents a study of 4H-SiC UV photodetectors based on p + n thin junctions. Two kinds of p + layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and the subsequent annealing) on the device characteristics. Aluminum and Boron dopants have been introduced by beam line and by plasma ion implantation, respectively. Dark currents are lower with Al-implanted diodes (2 pA/cm 2 @-5 V). Accordingly to simulation results concerning the influence of the junction thickness and doping, plasma B-implanted diodes give rise to the best sensitivity values (1.5x10-1 A/W @ 330 nm). Introduction During the past years there has been considerable interest in systems able to record very low light levels in the ultraviolet range in severe conditions of use. The advantage of Silicon Carbide (SiC) with respect to nitride alloys-the major wide band-gap semiconductor used today in industry-relies on three major points : a low residual doping for epitaxial layers (in the 10 14 cm-3 range and concentrations of residual defects/impurities at least one order of magnitude lower), a high thermal conductivity allowing high temperature operations, and a very good radiation hardness. It is then possible to use SiC for fabrication of devices capable to operate under extreme conditions. Photodetectors based on SiC allow to obtain good wavelength selectivity in the UV range, without any optical filters. Experimental The role of the p + emitter layer properties has been particularly studied in this paper. Among these properties, the doping and the thickness are thoroughly key parameters for controlling the device reliability. Photodetector simulations based on finite element method were performed, optimizing the design of the thin junctions for improvement of the light absorption and the carrier harvest. We also investigated the technological process giving rise to the dopant introduction into the SiC matrix. The comparison between standard ion implantation and pulsed-Plasma Immersion Ion Implantation (PIII) processes is expected to be fruitful, since PIII technology produced impressive results for Si solar cells in the UV range [1]. To our knowledge, PIII doping has never been carried out in SiC material. 4H-SiC n-type epilayers were either implanted with Aluminum by standard ion implantation at 27 keV, or with Boron by PULSION TM system (pulsed-plasma ion immersion)
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Submitted on : Sunday, September 1, 2019 - 5:05:13 PM
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Stéphane Biondo, Laurent Ottaviani, Mihai Lazar, Dominique Planson, Julian Duchaine, et al.. 4H-SiC P+N UV Photodiodes : A Comparison between Beam and Plasma Doping Processes. Materials Science Forum, Trans Tech Publications Inc., 2012, 717-720, pp.1203-1206. ⟨10.4028/⟩. ⟨hal-02275699⟩



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