2007 Fiscal Year Final Research Report Summary
Research and development of semiconductor lasers for optical communication with temperature stability
| Project/Area Number |
17360004
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | University of Tsukuba |
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Principal Investigator |
AKIMOTO Katsuhiro University of Tsukuba, Graduate school of Pure and Applied Sciences, Professor (90251040)
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| Co-Investigator(Kenkyū-buntansha) |
SAKURAI Takeaki University of Tsukuba, Graduate school of Pure and Applied Sciences, Assistant Professor (00344870)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Crystal Engineering / Optical Pronerties / Enerey Transfer / Rare Earth / LED |
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| Research Abstract |
GaN doped with rare-earth elements (RE) hold significant potential for applications in optical devices, since they show sharp intense luminescence which is only minimally affected by temperature variations. Among the various RE dopants, Er and Eu seems to be interesting, since Er yields IR luminescence at 1.5 μm which is used as optical communication and Eu yields red luminescence at 622 nm which has not been realized in commercially available light emitting devices (LEDs) that use InGaN active layers.
The Eu or Er-doped GaN thin films were grown on sapphire (0001) substrates by gas-source molecular beam epitaxy (GSMBE) using uncracked NH3 gas with 6N purity as the nitrogen source.
We have found single crystalline growth of Eu-doped GaN and nearly temperature independent luminescence at 622 nm originating from the intra-4f-4f transition of the Eu3+ ions. The red luminescence was analyzed and determined to be generated through trap-level-mediated energy transfer from the host GaN, and the
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external emission efficiency was estimated to be about 0.18 at room temperature when the Eu concentration was about 2 at. %. Extended x-ray absorption fine structure analysis has revealed that most Eu ions are located in substitutional Ga lattice sites with C_<3v> or lower symmetry. Three kinds of Eu incorporation sites have been shown to exist in Eu-doped GaN by studying photoluminescence, photoluminescence excitation, and two of them are excited by charge transfer and the other is excited through GaN host excitation. Therefore, site control is very important for the device fabrication. These results revealed that Eu-doped GaN could be a potential material for an active layer.
Similar results were also obtained for Er in GaN, that is, the luminescence intensity of Er is related with vacancy complex and Er is mainly incorporated into Ga site. However, there are multiple sites for Er in GaN and the interstitial Er may play an important role in luminescence emission through the GaN host excitation. The control of the incorporation site of Er is important as well as Eu to fabricate devices which is operated by carrier injection. These obtained results enable to realize LED and laser diodes. Less
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Research Products
(37 results)
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[Presentation] Pulsed laser annealing of GaN2006
Author(s)
D. Saito, T. Hattori, K. Akimoto, T. Sakurai
Organizer
The 53th Spring Meeting, the Japan Society of Applied Physics
Place of Presentation
Tokyo, Japan(2006)
Year and Date
2006-03-25
Description
「研究成果報告書概要(欧文)」より
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[Presentation] TEM observation of rare earth doped GaN2005
Author(s)
J. Seo, J. Sawahata, M. Takiguchi, D. Saito, K. Akimoto
Organizer
The 66th Autumn Meeting, the Japan Society of Applied Physics
Place of Presentation
Tokushima, Japan(2005)
Year and Date
2005-09-09
Description
「研究成果報告書概要(欧文)」より
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