| Project/Area Number |
06044021
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Tohoku University |
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Principal Investigator |
SUEMITSU Maki Research Institute of Electrical Communication, Tohoku University Associate Professor, 電気通信研究所, 助教授 (00134057)
末光 真希 (1995) 東北大学, 電気通信研究所, 助教授
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| Co-Investigator(Kenkyū-buntansha) |
SCHWAB Claud 国立科学研究所, 半導体物理学研究所, 教授
NIWANO Michio Research Institute of Electrical Communication, Tohoku University Associate Prof, 電気通信研究所, 助教授 (20134075)
CLAUDE Schwab C.N.R.S,Laboratory of physics and application of semiconductors Professor
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1995: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | GaAs / semi-insulating / point defect / optical properties / electron spin resonande / EL2 / photoquenching / photoconductivity / 硫化カリウム |
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| Research Abstract |
We have concentrated on the study of the mechanism of the photoquenching of EL2, a most important point defect in undoped semi-insulating GaAs. The photoquenching effect is a phenomenon in which all optical and electrical properties of EL2 are vanished by being irradiated with near-infrared lights at T<90K.The effect has been attributed to a transition of the EL2 defect into a metastable state, while some recent reports suggest contributions from other point defects than EL2. The clarification of the photoquenching effect is therefore of great importance in realizing high-quality GaAs crystals. What we found this year is as follows.
(1)The photoquenching of EL2 does not occur by itself. Contributions from other defects are essential. By testing a series of samples, in which only the carbon acceptor concentration is varied, we found a strong influence of the carbon acceptor on the activation of the photoquencing effect.
(2)By a quantitative analysis of the temperature dependence of the EL2 photoquenching, we found that a deep acceptor located at 70-80 meV above the valence band plays an essential role in the photoquenching effect.
(3)This level, named actuator level, accounts for both the carbon-concentration and the temperature dependence of the photoquenching effect, by assuming that the actuator level triggers the photoquenching of EL2 when it is neutral and triggers the photorecovery of EL2 when it is negatively ionized.
(4)By thermally-stimulated-current(TSC)measurements, we have confirmed the presence of a deep acceptor at the relevant position in the bandgap. Its charge state became neutral from the original ionized one after irradiation with the quenching light, consistent with our actuator level model.
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