Emission Characteristics of GaN-Based EL Device with AC Operation
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Emission Characteristics of GaN-Based EL Device with AC Operation Tohru HONDA and Hideo KAWANISHI Department of Electronic Engineering, Kohgakuin University 2665-1 Nakano-machi, Hachiohji, Tokyo 192-0015, Japan
Abstract GaN-based electroluminescence devices (ELDs) were fabricated using a GaN powder as an emission layer. The electroluminescence spectra of the GaN ELDs under AC operation were observed at room temperature. The emission characteristics of GaN-based ELDs were studied to compare the EL spectra and the cathodoluminescence (CL) spectra. It was clarified that the EL spectra were similar to the CL spectra of a GaN emission layer. The emission peaks in the EL spectra were shifted toward the high-energy side with increasing operation frequency.
Introduction The GaN-based III-V nitrides have received a great deal of attention for applications such as light-emitting diodes (LEDs) and laser diodes operating in the UV through green spectral regions [1, 2]. At the same time, rare-earth-doped GaN has also been studied for the current-injected electroluminescent devices (ELDs) grown by molecular-beam epitaxy (MBE) [3-5]. The inorganic ELDs operating in the UV and visible spectral regions have been extensively investigated for application to full-color flat display panels, because the major obstacle to practical use is the necessity of a pure-blue-emitting device. Recently, GaN: Er ELDs have been reported, suggesting that GaN is a suitable phosphors for ELDs operating in a short-wavelength (UV to green) spectral region [6]. Furthermore, for developing flat display panels using GaN-based ELDs, we must consider matching other color emitters with the structure of ELDs for integration into flat display panels. One of the best-matched structures is an AC-operation ELD, whose emitting layer is sandwiched between insulators. It is considered that epitaxial growth techniques are not suitable for the low-cost fabrication G11.13.1
of large ELD arrays, because epitaxial growth techniques such as metal-organic vapor phase epitaxy (MOVPE) and MBE require a high growth temperature typically higher than 800 °C. This high temperature results in surface cracks and so forth, because the ELDs consist of metals, insulators and emission materials, whose thermal coefficients are very different. And GaN growth temperature will warp standard flat display panel display glass-substrates. To realize the fabrication of a GaN layer at a low temperature, GaN powder was deposited for the light-emission layers. Although the synthesis of GaN requires a high temperature, the fabrication of an emission layer using GaN powder by deposition can be achieved at a low temperature. In this study, AC-operation ELDs using GaN powder for the emission layer were fabricated to examine the possibility of GaN-based ELDs and their fabrication process with a low temperature. Experimental GaN powder, which was produced using a nitridation technique of gallium metal, was used in this study. The purity of the powder used as the source was 99.9%; the impurity was main
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