Enhancement of Er optical efficiency through bismuth sensitization in yttrium oxide

• Published in: Applied physics letters 2015-07, Vol.107 (4)
• Main Authors: Scarangella, Adriana, Reitano, Riccardo, Franzò, Giorgia, Priolo, Francesco, Miritello, Maria
• Format: Article
• Language: English
• Subjects: Applied physics; BISMUTH; BISMUTH IONS; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Clustering; CROSS SECTIONS; EFFICIENCY; Emitters; Energy transfer; Erbium; ERBIUM IONS; EXCITATION; Excitation spectra; MAGNETRONS; Optical activity; PHOTOLUMINESCENCE; Photonics; Photovoltaic cells; PHOTOVOLTAIC EFFECT; Silicon; Solar cells; SPECTROSCOPY; SPUTTERING; THIN FILMS; VALENCE; Yttrium oxide; YTTRIUM OXIDES
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4927833

The process of energy transfer (ET) between optically active ions has been widely studied to improve the optical efficiency of a system for different applications, from lighting and photovoltaics to silicon microphotonics. In this work, we report the influence of Bi on the Er optical emission in erbium-yttrium oxide thin films synthesized by magnetron co-sputtering. We demonstrate that this host permits to well dissolve Er and Bi ions, avoiding their clustering, and thus to stabilize the optically active Er3+ and Bi3+ valence states. In addition, we establish the ET occurrence from Bi3+ to Er3+ by the observed Bi3+ PL emission decrease and the simultaneous Er3+ photoluminescence (PL) emission increase. This was further confirmed by the coincidence of the Er3+ and Bi3+ excitation bands, analyzed by PL excitation spectroscopy. By increasing the Bi content of two orders of magnitude inside the host, though the occurrence of Bi-Bi interactions becomes deleterious for Bi3+ optical efficiency, the ET process between Bi3+ and Er3+ is still prevalent. We estimate ET efficiency of 70% for the optimized Bi:Er ratio equal to 1:3. Moreover, we have demonstrated to enhance the Er3+ effective excitation cross section by more than three orders of magnitude with respect to the direct one, estimating a value of 5.3 × 10−18 cm2, similar to the expected Bi3+ excitation cross section. This value is one of the highest obtained for Er in Si compatible hosts. These results make this material very promising as an efficient emitter for Si-compatible photonics devices.