| Co-Investigator(Kenkyū-buntansha) |
MOMOSE Hideki Low Temperature Center, Research Associate, 低温センター, 助手 (80260636)
MORI Nobuya Faculty of Engineering, Department of Electronic Engineering, Research Associate, 工学部, 助手 (70239614)
MORIFUJI Masato Faculty of Engineering, Department of Electronic Engineering, Research Associate, 工学部, 助手 (00230144)
TANIGUCHI Kenji Faculty of Engineering, Department of Electronic Engineering, Associate Professo, 工学部, 助教授 (20192180)
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| Research Abstract |
Quasi-one-dimensional electrons in quantum wires give various interesting features in transport and optical properties. Such electron gas may be formed by constricting two-dimensional electron gas in heterointerfaces by using gate electrodes or by etching the side walls. Such Quasi-one-dimensional electron gas exhibit different electron-phonon interactions due to the singularity of the density of states, and thus we can expect a very interesting feature of electron transport. At low temperatures, it is well known that such electrons show ballistic transport, interference effects, quantization of conductivity, quantum fluctuation and so on. In this research project we will concern with investigation of electronphonon interaction in quantum wires at high temperatures and also with theoretical formulation and experimental observation of magnetophonon resonance. The obtained results are summarized in the following.
1. We derived magnetoconductivity of quasi-one-dimensional electron gas by u
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sing Kubo formula. In a narrow quantum wire with parabolic confinement potential, energy spacing hOMEGA, the magnetoconductivity exhibits extrema at resonance NhROO<W^2_+OMEGA^2>=hw_o, where w_c=eB/m^* and N=1,2,3, -The magnetoconductivity is found to consist of two dominant terms, the one, sigma_<ep>, due to the scattering of electrons located near the center of the quantum wire by LO phonons resulting in maxima of the magnetoconductivity at the resonance, and the other, sigma_<po> due to the disturbance of the skipping motion of electrons near the edge of the quantum wire giving rise to minima in the magnetoconductivity. Experiments have been carried out in quantum wires with different structures, and revealed maxima in the magnetorisistance(p_<xx>=1/sigma_<xx>)in the temperature range 100-200K,which indicates the term sigma_<po> dominates. 2. We fabricated quantum wires by using electron beam lithography and by laser beam holography. Also we prepared optical masks for processing quantum wires. 3. Experimental observation revealed clear Shubnikov-de Haas oscillations at 4.2 K and clear oscillatory structures at higher temperatures, which show a good agreement with the theoretical prediction. The analysis gives the effective mass and confinement potential. 4. We prepared quantum wires with Schottky gates and low temperature measurements gives quasi-one-dimensional nature of electrons with confinement potential of 05 meV.5. We carried out cyclotron resonance measurements of GaAs/AlAs short period superlattices at high magnetic fields and observed the resonance of electrons in the zone-folded X_z conduction band. We found that the cross-over of the G and X_z conduction bands occur at the monolayr number n=12.6. We fabricated p-i-n diodes of GaAs/AlAs superlattices and succeeded in the first observation of Zener tunneling associated with Wannier-Stark states. Less
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