Electroluminescent devices based on Er-doped Si nanoclusters
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Electroluminescent devices based on Er-doped Si nanoclusters F. Priolo1, F. Iacona2, D. Pacifici1, A. Irrera1, M. Miritello1, G. Franzò1, D. Sanfilippo3, G. Di Stefano3, and P.G. Fallica3 1
INFM and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania, Italy; 2CNR-IMM, Sezione di Catania, Stradale Primosole 50, I-95121 Catania, Italy; 3 STMicroelectronics, Stradale Primosole 50, I-95121 Catania, Italy ABSTRACT The electroluminescence (EL) properties of Er-doped Si nanoclusters (nc) embedded in metal–oxide–semiconductor devices are investigated. It is shown that, due to the presence of Si nc dispersed in the SiO2 matrix, an efficient carrier injection occurs and Er is excited producing an intense 1.54 µm room temperature luminescence. The EL properties as a function of the current density, temperature and time have been studied in details, elucidating the radiative and non-radiative de-excitation properties of the system. We have also estimated the excitation cross section for Er under electrical pumping finding a value of ∼1×10-14 cm2. This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si nc under optical pumping, and quantum efficiencies of ∼1% are obtained at room temperature in these devices. These data will be presented and the impact on future applications discussed.
INTRODUCTION Silicon has been considered for a long time unsuitable for optoelectronic applications, because, due to the indirect nature of its energy band gap, it is a highly inefficient light emitter. Among the different approaches developed to overcome this problem, quantum confinement in Si nanostructures and rare earth doping of crystalline Si have received a great attention. Si nanoclusters (nc) embedded in SiO2 have attracted in the last years the interest of the scientific community as a new promising material for the fabrication of a Si-based light source [1-5] based on quantum confinement effects. Alternatively, Er-doped crystalline Si has been extensively studied to take advantage of the radiative intra-4f shell Er transition, and room temperature operating devices with efficiencies around 0.05% have been achieved [6]. Recently, the coupling of the two approaches has produced interesting results. In fact, Er-doped Si nc are efficient light emitters at 1.54 µm [7-10], since Si nc in presence of Er act as sensitizers for the rare earth. In spite of the large amount of experimental data present in the literature on the photoluminescence (PL) properties of Si nc, only a few papers have reported the electroluminescence (EL) characteristics of this material [11-18], mainly due to the difficulties of carrier injection in a semi-insulating material. In the present work, the feasibility of efficient and stable Er-doped Si nc based light emitting devices operating at room temperature will be demonstrated. We will show that it is possible to obtain an efficient carrier injection at low voltage, and a strong EL signal at 1.54 µm even at room te
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