Phosphorous and Boron Incorporation and its Effect on Optical Properties of Ge:H and Si 0.01 Ge 0.99 :HFilms Deposited b
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Phosphorous and Boron Incorporation and its Effect on Optical Properties of Ge:H and Si0.01Ge0.99:HFilms Deposited by LF PECVD Nery Delgadillo1, Andrey Kosarev2, Afonso Torres2, Lancelot Garcia1 and Brian Gonzales1 1
University Autonomy of Tlaxcala, Faculty of Engineering and Technology, Calzada Apizaquito s/n, km. 1.5, ApizacoTaxcala, 90300, Mexico Email: [email protected] 2
National Institute for Astrophysics, Optics and Electronics, L.E.Erro No.1, Col. Tonantzintla, Puebla, 72840, Mexico
ABSTRACT Deposition conditions that provided low absorption related to both band tail and deep localized states have been found for both materials Ge:H and Si1YGeY:H. Phosphorous incorporation on Si0.01Ge0.99:H films and boron incorporation on Ge:H films were deposited by low frequency plasma-enhanced chemical vapour deposition (LF PECVD). The phosphorous incorporation in solidphase was observed to preferential with the increase of the doping in the gas phase to 2.5 %, and 2.5% to 4% was observed preferential Si0.01Ge0.99 film, boron incorporation in solid phase increase linearly with the increase of the doping gas phase. The content of solid phase was characterized by Secondary ion mass spectrometry (SIMS) profiling. Hydrogen concentration in the films was determined from Fourier transform infrared spectroscopy (FTIR) and SIMS measurements. Optical measurements provided optical gap, localized states, and band tail. A significant reduction of both band tail and deep localized states were observed at boron incorporation in solid phase = 0.004% on Ge:H films and the same were observed at phosphorous incorporation in solid phase = 0.29% on Si0.01Ge0.99:H films. Keywords: amorphous, film, Ge, plasma-enhanced CVD (PECVD), optical properties INTRODUCTION Hydrogenated Silicon-Germanium (SiYGeY-1:H) and Germanium films (Ge:H) deposited by plasma at low frequency are of great interest for their potential applications in many electronic devices such as low band gap solar cells, photo-detectors, thermo-photovoltaic, un-cooled bolometer and p-i-n detector [1-6], but with plasma deposited Ge:H and SiGe:H films usually demonstrate worse electronic properties in comparison with those of Si:H films. The deposition conditions providing the best electronic properties for silicon films did not allow to prepare good quality Ge:H and SiGe:H films. Previously [7] we have demonstrated with low frequency plasma-enhanced chemical vapour deposition (LF PECVD) method, fabrication of Ge:H and SiGe:H films that in solid state have 3% of silicon and 97 % of germanium with low both tail and deep localized states absorption. These films are suitable for doping and we studied practically doping of Germanium films, were only a few papers have been reported [8-10] in comparison of phosphorous and boron doping of a-Si:H films. This work is the study of the effect of incorporation of boron and phosphorous in wide range of concentrations and its effect on optical properties of germanium (Ge:H) and silicongermanium, practically germanium (Si0.01Ge0.99:H)films deposi
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