音 賢一

We investigate the influence of electron-electron interactions on cyclotron resonance (CR) of two-dimensional electron systems in tilted magnetic field. It is known that the electron-electron interactions affect the CR spectra in systems that have more than two cyclotron frequencies. In this study, this multi-component system is realized by applying the tilted magnetic field; the tilted magnetic field induces the resonant subband-Landau level coupling (RSLC) and a splitting of the CR spectrum is observed. Observed anomalous CR spectra cannot be explained by the RSLC with the single-electron picture. Present theoretical treatments cannot account for the result of our experiment. (C) 2003 Elsevier Ltd. All rights reserved.

Single AlGaAs and GaAs quantum wires (QWRs) have been investigated by micro-photoluminescence (micro-PL). The micro-PL spectra of the GaAs QWR reveal that the GaAs QWR consists of a number of sharp peaks with a full-width at half-maximum (FWHM) of several hundreds mu eV, which is similar to the results of previous reports. In contrast, micro-PL spectra of the AlGaAs QWR exhibit only one peak with a FWHM of similar to 1 meV. indicating homogeneous QWR. The CL measurements are consistent with the results of the micro-PL measurements. The different features of the micro-PL spectra of the GaAs and AlGaAs QWR come from fluctuations in the thickness of the QWR. Therefore, the AlGaAs homogeneous QWRs are expected to exhibit intrinsic one-dimensional properties of the QWR and to clarify various properties of one-dimensional systems, such as carrier transportation in the QWRs. (C) 2001 Elsevier Science B.V. All rights reserved.

縦型結合ドット配列の遠赤外磁気光吸収測定において, 縦方向に結合した2つのドット中の電子の2本の共鳴吸収信号を観測した。この共鳴ピークのうち, 表面近傍に位置するドットからの共鳴ピークは光励起下ではシフトすることを観測し, このシフトがドット間の結合変化からの影響も含むことを示すことが出来た。光励起下でこのピークシフトの測定より, 縦型結合ドット中の電子状態への結合変化の影響を詳細に調べ, 議論する。

We have investigated CdSe quantum dots (QDs) by micro photoluminescence (PL). To reduce the number of QDs to be observed, Al masks with sub-micron size apertures are deposited on the sample surfaces, which make it possible to repeatedly trace the same excitation position in taking temperature dependent micro-PL spectra. Resolved sharp lines having linewidth similar to 500 mu eV are observed. The results of temperature dependence reveal that the linewidths of QDs broaden with increasing temperature, which is considered to come from lifetime broadening of ground state by absorption of phonons. The linewidth broadening depends on the peak energy position of the QDs. The linewidths of lower-energy lines corresponding to larger size QDs, are more temperature-dependent than those of higher-energy lines corresponding to smaller ones. The different linewidth broadening can be qualitatively explained by taking into consideration of different energy level spacing between discrete states of the QDs. (C) 2000 Elsevier Science B.V. All rights reserved.

In the far-infrared response of dot structures, a shift of the resonance peak of electrons in a dot can be clearly observed under pulsed photoexcitation. The peak shift is interpreted by a potential modulation due to photoexcitation. In a dot array fabricated on a double heterostructure, the potentials of vertically aligned two dots are also modulated. The modulation is different from each other. This potential modulation gives the possibility that the vertical coupling between two dots can be controlled by photoexcitation.