Project/Area Number  08650380 
Research Category 
GrantinAid for Scientific Research (C)

Section  一般 
Research Field 
Electronic materials/Electric materials

Research Institution  Osaka University 
Principal Investigator 
MORI Nobuya Osaka University, Faculty of Engineering, Lecturer, 工学部, 講師 (70239614)

CoInvestigator(Kenkyūbuntansha) 
MOMOSE Hideki Osaka University, Low Temperature Center, Research Associate, 低温センター, 助手 (80260636)
MORIFUJI Masato Osaka University, Faculty of Engineering, Research Associate, 工学部, 助手 (00230144)
HAMAGUCHI Chihiro Osaka University, Faculty of Engineering, Professor, 工学部, 教授 (40029004)

Project Fiscal Year 
1996 – 1997

Project Status 
Completed(Fiscal Year 1997)

Budget Amount *help 
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)

Keywords  tunneling effect / quantum dot / Coulomb interaction / electronphonon interaction / ionized impurity / resonant tunneling / extact diagonalization / single electron device / トンネル効果 / 量子ドット / クーロン相互作用 / 電子フォノン相互作用 / イオン化不純物 / 共鳴トンネル効果 / 厳密対角化法 / 単電子素子 / トンネル行列要素 / トンネル現象 / 共鳴トンネル / 半導体ヘテロ構造 
Research Abstract 
In order to analyze the effect of electronelectron interaction on measuring the probability density of quantum confined states, a computer program has been made which numerically calculates the exact Nelectron states in a quantum dot by diagonalizing the Hamiltonian matrix. Electronic structures in circular, elliptic and triangular shaped quantum dots containing single or N electrons have then been calculated using the computer program. In a circular quantum dot, the addition energy shows a clear structure as a function of N due to the shell filling and the spin polarized half filling. In an elliptic quantum dot, however, the structure is found to be diminished, which is attributed to the splitting of the degenerated singleparticle states due to the asymmetric confining potential. Tunneling matrix elements through a quantum dot have been calculated by using the eigen states evaluated with the exact diagonalization. Energy relaxation time through longitudinalacoustic phonon emission has also been calculated for a GaAs quantum dot with N electrons (from N=1 to 4), where the electrons in a narrow quantum well are confined by a parabolic confining potential. The electronic states are numerically evaluated by taking into account of the Coulomb interaction between the electrons, and the relaxation time is estimated by using the Fermi's golden rule. As the number of electrons increases, the energy levels become dense, and the number of relaxation channels drastically increases. From the evaluation of the relaxation time associated with all the relaxation channels, several relaxation processes are found to be accelerated by indirect process through some intermediate states between the initial and the final states.
