Showing papers by "Keisuke Ohdaira published in 2004"
TL;DR: In this paper, the type-I and type-II band alignments were successfully controlled by changing composition and growth temperature in AlInAs/AlGaAs self-assembled quantum dots.
Abstract: Type-I and type-II band alignments were successfully controlled by changing composition and growth temperature in AlInAs/AlGaAs self-assembled quantum dots. The Al composition dependence of the photoluminescence peak shift clearly indicated the crossover from type-I to type-II band line up and a long decay time of ∼30 ns was obtained by time-resolved photoluminescence at 8 K for the sample with type-II band alignment grown under optimized conditions. A much longer decay component of ∼500 ns was also observed from the same structure, but it may be due to slow relaxation of carriers trapped in AlGaAs matrix.
10 citations
TL;DR: In this paper, the authors measured magneto-photoluminescence (PL) spectra in type-II heterostructures of GaAs/AlAs in high magnetic fields up to 40 T under a uniaxial pressure.
Abstract: We measured magneto-photoluminescence (PL) spectra in type-II heterostructures of GaAs/AlAs in high magnetic fields up to 40 T under a uniaxial pressure. We observed a remarkable decrease of the integrated magneto-PL intensity with increasing magnetic field at 4.2 K . With increasing temperature or excitation laser power, however, the field-induced decrease of the integrated PL intensity became lesser amount. The experimental observation strongly suggests that electrons and holes are localized in minima of the fluctuating potential due to the interface roughness. We can infer that this is a general feature of the indirect excitons which comprise spatially separated electrons and holes.
1 citations
TL;DR: In this article, magnetic field dependence of photoluminescence (PL) characteristic of type-II quantum dots (QDs) was observed in AlInAs/AlGaAs self-assembled QDs.
Abstract: Magnetic-field dependence of the photoluminescence (PL) characteristic of type-II quantum dots (QDs) was observed in AlInAs/AlGaAs self-assembled QDs. Parameters of the exciton in this system such as a lateral confining energy, a reduced mass and an average radius estimated from the magnetic-field dependence clearly indicated that type-II excitons with holes confined in QDs and electrons in AlGaAs matrix were formed. The PL intensity change both in the Faraday and Voigt configurations, which was well-explained in terms of the shrinkage of electron and hole wave functions and resulting change of their overlap, indicated that electrons in AlGaAs matrix were bound at the top or the bottom of QDs where holes were trapped. The competition between the increased overlap of electron and hole wave functions and the transition of band alignments from type-I to type-II induced by high magnetic fields was also found to provide an anomalous magnetic field dependence of the PL intensity in a particular sample where man...