2002 Fiscal Year Final Research Report Summary
Growth of nitride semiconductor quantum structures and their application for blue vertical-microcavity lasers
| Project/Area Number |
12650037
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NISHIOKA Masao The University of Tokyo, Institute of Industrial Science, Research associate, 生産技術研究所, 助手 (70218121)
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| Co-Investigator(Kenkyū-buntansha) |
ARAKAWA Yasuhiko The University of Tokyo, Research Center for Advanced Science and Technology, Professor, 先端科学技術研究センター, 教授 (30134638)
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| Project Period (FY) |
2000 – 2002
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| Keywords | nitride semiconductor / VCSELs / microcavity / ITO |
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| Research Abstract |
In this research, we established the fundamental technologies for realizing blue-violet vertical-cavity surface-emitting lasers (VCSELs).
First, with precise control of growth conditions, electrically conductive n-DBRs with high reflectivity were successfully obtained. We also proposed n-AlGaN/n-GaN superlattice DBRs in which n-AlGaN/n-GaN superlattices are used instead of n-AlGaN quarter-wave layers in conventional DBRs. A 26-period DBR with this novel structure revealed to have reflectivity as high as 94.5%, and to be able to suppress cracking.
Second, we utilized an indium tin oxide (ITO) transparent p-contact and achieved efficient injection of holes. Rapid thermal annealing under nitrogen ambient can improve optical transmittance and electrical conductivity of a sputtered ITO film simultaneously.
Furthermore, we fabricated and demonstrated InGaN vertical microcavity light emitting diodes (LEDs) as a basic structure toward the current injected blue-violet VCSELs. The emission peak wid
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th of the fabricated device was 3.6 nm, while the emission directionality was rather improved than conventional LEDs. These optical characteristics showed that microcavity effects were actually occurred in these LEDs. In addition, series resistances of the LEDs could be reduced with the n-type superlattice DBR. These results are assumed to be breakthroughs to realize current injected blue VCSELs.
On the other hand, we also demonstrated for the first time the enhancement of spontaneous emission coupling factor β in nitride-based vertical microcavity surface emitting laser at room temperature. From input-output measurements and analysis of the rate equations, the β of the lasing mode is estimated to be 1.6 × 10^<-2> by assuming the internal quantum efficiency η of 10% and the transparency carrier concentration of 1.0 × 10^<19>cm^<-3>. The estimated β can be well accounted for by a simple theoretical model. High quality microcavity can be fabricated with nitride semiconductors, which is very promising for further application such as single photon emitters. Less
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