Supersonic-Free-Jet CVD Growth of Dy-doped Silicon Films for 1.3 Micron LED
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Supersonic-Free-Jet CVD Growth of Dy-doped Silicon Films for 1.3 Micron LED Shinji Kawai, Koji Matsutake, Fumiya Watanabe and Teruaki Motooka Department of Materials Science and Engineering, Kyushu University 6-10-1 Hakozaki, Fukuoka 812-8581, Japan ABSTRACT We have investigated epitaxial growth of dysprosium (Dy)-doped silicon (Si:Dy) thin films for fabrication of 1.3 µm light-emitting diodes (LEDs) using supersonic-free-jet CVD. The 700-nm-thick Si:Dy films are grown on p+-type, p-type, and n-type Si(100) at a substrate temperature of 800 for 90 min. The doping concentrations of Dy atoms range from 1018 to 19 -3 10 cm at the surface region of the film measured by the secondary ion mass spectrometry (SIMS). The particles with average size ~200 nm form at the surface of the film and it suggests the possibility to form Si-nanoparticle (Si quantum dots) from atomic force microscopy (AFM) observation. From the electrical measurements at room temperature, the metal (Al)-Si:Dy junction is a Schottky contact and Dy introduces donor states in Si.
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INTRODUCTION Si-based optoelectronics has become a very important and interesting technology for the integration of photonic and electronic devices on a single Si chip [1-5]. This new technology requires Si-based new photonic materials on Si substrates. However, it faces the lack of practical light sources such as lasers and light-emitting diodes (LEDs) because Si itself cannot efficiently emit light due to its indirect band gap. Therefore, many approaches to obtain efficiently light emission from Si are under intense investigation because of many potential applications. One promising way is rare-earth doping of Si, especially erbium (Er). Because Er3+ ions in Si exhibits 4 a sharp luminescence at 1.54 µm (4I13/2 I15/2). This wavelength coincides with the minimum absorption wavelength of silica optical fibers. The first demonstration of Er-related 1.54 µm electroluminescence (EL) at 77 K was reported by Ennen et al.[6] In 1994, a sharp 1.54 µm-EL was observed from room temperature operating reverse-biased Er-doped Si LEDs [7,8]. On the other hand, there has been little work with Si-based photonic materials emitting 1.3 µm light. This emission wavelength coincides with the minimum dispersion wavelength of silica optical fibers. Dy3+ is one of the most interesting candidates in rare-earth ions with emission of 1.3 µm light [9-13]. Recently, Dy-doped chalcogenide glasses have been applied in a 1.3 µm optical fiber amplifier [9,10,12]. Figure 1 shows the energy band diagram and 1.3 µm transition of Dy3+ 6 ion. Its 6H9/2+6F11/2 H15/2 transition (first excited ground state) corresponds to an emission wavelength of 1.3 µm. In this paper, we report supersonic-free-jet CVD growth of Si:Dy thin films for the fabrication of 1.3 µm LEDs and their electrical properties. Supersonic-free-jet CVD method is a new CVD technique to precisely control the film thickness and to grow the film in high vacuum condition adjusting the pulse width and frequency. Our group has developed this method for Si
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