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Nobuyuki Koguchi 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
Recent progress on the direct formation of GaAs/AlGaAs and InGaAs/GaAs QDs systems by droplet epitaxy are reviewed. The droplet epitaxy is promising for the fabrication of compound semiconductor quantum dots not only in a lattice-mismatched system but also in a lattice-matched system. By using this method, QDs samples without wetting layers are realized. We also review our recent progress toward the fabrication of site-controlled QDs by using droplet epitaxy on GaAs (001) with well-aligned nano-holes developed by combination of Atomic Force Microscopy (AFM) tip-induced oxidation and atomic hydrogen etching technique.en
Auger processes in InGaAs QDs grown by droplet method
이주인,Il Ki Han,F. Minami,Nobuyuki Koguchi,T. Kuroda 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.42
We present the carrier dynamics of InGaAs quantum dots with and without cladding layers grown by heterogeneous droplet epitaxy. Time-resolved photoluminescence spectroscopy showed double exponential decays for the rst excited states, including an initial fast decay, of highly excited quantum dots with cladding layers in contrast to the single exponential decay in quantum dots without cladding layers. Moreover, the GaAs barriers had slow rise times of about 220 ps, which corresponded to the initial fast decay time of the rst excited states of quantum dots. These results provide evidence of Auger processes between the carriers in the GaAs barriers and those in the rst-excited states of quantum dots.
Optical Properties of GaAs/AlGaAs Quantum Dots Grown by Droplet Epitaxy with Post-Growth Annealing
Chang Myung Lee,Joo In Lee,Dong-Han Lee,Jae-Young Leem,한일기,Nobuyuki Koguchi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.42
We have studied the post-annealing eects on the optical properties and the spectral homogeneous broadening of GaAs/AlGaAs quantum dots (QDs) fabricated by modied droplet epitaxy. The photoluminescence (PL) intensity of the QDs increased drastically and the peak energy shifted toward high energy, by about 69 meV, after annealing. These eects may be caused by the improved crystallinity of the QD systems, the size reduction of the QDs, and/or composition changes in the QDs by post-annealing. From precise examination of the micro-PL spectra under weak excitation conditions, the minimal homogeneous linewidth of the QDs was estimated to be 1.45 1.6 meV at 77 K.
종수 김,D. Y. Lee,Gu-Hyun Kim,H. K. Choi,I. H. Bae,J. I. Lee,Jae-Young Leem,Jin Soo Kim,Minhyon Jeon,Nobuyuki Koguchi,S. H. Lee,S. I. Ban,S. K. Kang 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
The structural and optical properties of non-wetting layer InAs quantum dots (QDs) have been investigated by transmission electron microscopy (TEM), photoreflectance (PR) and photoluminescence (PL). By alternate depositing 0.83 $\sim$ 1.2 ML InAs and 1.2 $\sim$ 1.5 ML Ga(Al)As with different period on GaAs surface, the wetting layer of InAs QDs was controlled. TEM images clearly show the formation of QDs by using quasi monolayer (QML) deposition and non-wetting layer of InAs QDs. The QDs formed by using QML could not be grown by Stranski-Krastanov (S-K) growth. In PR measurement, the wetting layer transition is not observed for all the QML QDs. These QML QDs growth mechanisms are explained by adatom migration effect due to surface chemical potential.