| Project/Area Number |
62540264
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物性一般（含極低温･固体物性に対する理論）
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| Research Institution | Kobe University |
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Principal Investigator |
AOKI Kazunori Faculty of Engineering, Kobe University, assistant prof., 工学部, 助手 (80112077)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Shinji Faculty of Engineering, Kobe University, associate prof., 工学部, 助教授 (50107348)
YAMAMOTO Keiichi Faculty of Engineering, Kobe University, prof., 工学部, 教授 (80031087)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | chaos / semiconductor / high-purity n-GaAs / current filament / impact ionization / negative differential resistivity / bifurcation process / 周期倍分岐 / GaAS / ヒステリシス / 外部変調 / 分岐現象 / 外因性クライシス / フーリェスペクトル |
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| Research Abstract |
The purpose of the present research was to make clear the physical mechanism and the statistical properties (bifurcations, fractal dimension, etc.,) for the chaotic phenomena observed in a semiconductor (high-purity n-GaAs). Along the research schedule, we carried out the experiments and the computer simulations, and the research aim was almost succeeded.
All the experiments were done at 4.2 K, by using n-gaas with ohmiccontacts. By applying the dc voltage of about 1.2 V, the negative differential resistivity was observed due to the impact ionization of the neutral shallow donors, which results in the current-filament formation. Bifurcation process and chaos of the current filament was studied by applying dc+ac bias in the hysteresis region of the S-shaped static I-V curve. The phase diagram was investigated as functions of cotrol parameters of the driving frequency f_o (0.9 MHz f_o 1.4 MHz) and the dc bias V_o (2.1 V V_o 2.9 V). As a result, we found that many periodic islands are embedded in the chaotic sea; the bifurcation shows a periodic-chaotic alternation bifurcation sequence 1T- C- 7T - C-6T- C - ... - 3T - C - 2T- 1T (T:period, C:chaos) by increasing V_o (f_obeing fixed). Similar result was obtained by computer simulation. From the phase portraits of the chaotic oscillation, we estimated the correlation dimension to be 2.19 0.1, and K_2 entropy to 0.29+0.07.
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