Synthesis and Optical Characterization of Er-Doped GaN Low-Dimensional Structures
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Synthesis and Optical Characterization of Er-Doped GaN Low-Dimensional Structures Joan Carvajal1, Magdalena Aguilo2, Francesc Diaz2, and J. Carlos Rojo1 1 Materials Science & Engineering, State University of New York, Stony Brook, New York, 11794 2 Physics and Crystallography of Materials (FiCMA), Universitat Rovira i Virgili, Tarragona, 43007, Spain ABSTRACT Low-dimensional structures of GaN doped with Er and with rod shape have been synthesized on the surface of a silicon (001) substrate using a catalyst-assisted chemical vapor deposition technique. Ga, NH3 and Er were used as the gallium, nitrogen and erbium sources, respectively. The low-dimensional nanostructures were characterized spectrocopically analyzing the hypersensitive 4G11/2 and 2H11/2 bands of Er3+ located at 375 and 425 nm, respectively. Green and near-infrared (IR) emission produced by these Er-doped GaN low-dimensional structures has been observed under excitation at 488 and 543 nm using confocal microscopy. INTRODUCTION Doping semiconductor materials with lanthanide (Ln) ions is a very promising approach to generate temperature-stable, near-IR-light emission at well-defined wavelengths [1]. Using a semiconductor as the lattice host, the Ln ion can be activated by means of electronic processes. The excitation of the optically active ion can be triggered by impacts with the hot carriers of the semiconductor or nearby electron-hole recombinations. This latter mechanism generates a nearly ideal optical emission that can even be amplified [2]. Ln-doped narrow-bandgap semiconductors, such as Si or GaAs, have been hampered to achieve efficient optical emission at room temperature due to both the low solubility of the Ln ions in these host materials, and the severe quenching that their photoemission suffers at room temperature [2]. Among Ln ions, Er3+ is of particular interest for applications in optical communications at long distances due to its efficient emission near 1.5 µm, lying within the lowloss window of silica fibers [1]. The high absorption by the eye’s aqueous humor of light with wavelengths lying in this region of the IR spectrum also makes this emission very attractive for safety-eye radiation in industrial applications [3]. The thermal quenching that Ln ions suffer in Ln-doped semiconductors decreases as the bandgap of the semiconductor increases [4]. Thus, wide bandgap semiconductors are more desirable hosts for Ln ions than narrow bandgap semiconductors, such as Si and GaAs. Among wide-bandgap semiconductors, gallium nitride, GaN, represents a very attractive host choice for Ln ions. GaN finds application in the fabrication of short-wavelength emitters and detectors, and high-frequency, high-power, and high-temperature electronics [5,6]. The integration of Ln-doped GaN with GaN-based electronics and optoelectronics could enable the development of new costefficient technologies for optical communications. Er-doped GaN exhibits a strong emission from the lowest excited state at 1.5 µm [1]. Other photoemissions in the green at 5
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