Studies on CdS thin-film green light-emitting diodes
| Project/Area Number |
12650332
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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 |
電子デバイス・機器工学
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| Research Institution | Iwate University |
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Principal Investigator |
KASHIWABA Yasube Iwate Univ., Electrical & Electronic Eng., Assoc. Prof., 工学部, 助教授 (30003867)
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| Co-Investigator(Kenkyū-buntansha) |
BABA Mamoru Iwate Univ., Electrical & Electronic Eng., Prof., 工学部, 教授 (20111239)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | CdS thin film / p-type CdS / pn junction / LED / XPS / photoluminescence / photovoltaic cell / p型CdS / pn接合ダイオード / ダイオード |
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| Research Abstract |
CdS is an attractive material for a green light-emitting diode because of its direct band gap of 2.4 eV at room temperature. However, attempts to fabricate a CdS light-emitting diode have not been successful because the formation of p-type CdS has proven to be very difficult. We previously reported in detail the p-type characteristics of a Cu-doped CdS (CdS : Cu) film fabricated by vacuum deposition. The purpose of this study was to fabricate green light-emitting diodes using CdS thin films and to determine role of Cu in the Cu-doped CdS films. The following results were obtained.
1. X-ray photoelectron spectroscopy(XPS) showed that the p-type characteristics of CdS : Cu films are due to a Cu acceptor in which some of the Cd^<2+> are substituted by Cu^+ in unit cells of CdS.
2. Thin-film diodes composed of Cu-doped p-type CdS and non-doped n-type CdS films showed light emissions only under the condition of a forward current pulse at 77 K. The colors of emitted light changed within the range of blue-green to red depending on the fabrication conditions and forward current density. The spectra of the lights were broad and had small peaks near the absorption edge of CdS. It is thought that the light emission of the diode is generated by a p-CdS : Cu/n-CdS homojunction and that the change in the color of emitted light is caused by the mixing of two transition processes in CdS films, the interband and/or near-interband transitions and the transition through deep and broad Cu levels.
3. Photoluminescence (PL) of CdS and CdS : Cu films has been measured at room temperature. The results show that energy levels of the doped Cu are distributed in a wide range up to about 1 eV above the valence band edge.
4. Cells with the same structure as that of the light-emitting diode showed photovoltaic effects, and the efficiency of the cells was over 8.5 %. It is also thought that the photovoltaic effect of the cells is caused by a p-CdS/n-CdS homojunction.
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Report
(3 results)
Research Products
(13 results)
