AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS-WeP

Paper NS-WeP6
InGaAs Quantum Dots fabricated by Separated-Phase Enhanced Epitaxy with Droplets (SPEED)

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: T. Mano, National Research Institute for Metals, Japan
Authors: T. Mano, National Research Institute for Metals, Japan
K. Watanabe, National Research Institute for Metals, Japan
S. Tsukamoto, National Research Institute for Metals, Japan
Y. Imanaka, National Research Institute for Metals, Japan
T. Takamasu, National Research Institute for Metals, Japan
H. Fujioka, University of Tokyo, Japan
G. Kido, National Research Institute for Metals, Japan
M. Oshima, University of Tokyo, Japan
N. Koguchi, National Research Institute for Metals, Japan
Correspondent: Click to Email
Highly uniform InGaAs quantum dots (QDs) were successfully grown by Separated-Phase Enhanced Epitaxy with Droplets (SPEED) method. The SPEED is a novel method for self-organizing growth with highly dense Ga droplets produced by Droplet Epitaxy.@footnote 1@ All samples were grown on GaAs (001) substrates by molecular beam epitaxy method. After the growth of a GaAs buffer layer, an As-stabilized c(4x4) surface was formed as an initial surfaces. On this surface, 1.75ML of Ga, 2.5ML of In, and 50ML of Ga were supplied at 200°C, in order to compensate the 1.75ML excess As on c(4x4), to form the InGa droplets, and to form the highly dense Ga droplets surrounding the InGa droplets, respectively. After the formation of these droplets, which were very uniform in size, As flux was supplied at 200°C for crystallization and the sample was annealed at 500°C. At that time, the highly dense Ga droplets prevented the 2-dimensinal growth of the InGaAs and the separated-phase effect of InGaAs-GaAs was enhanced. Finally, a GaAs capping layer was grown. To confirm the effect of highly dense Ga, a reference sample was also fabricated with the same procedure except for the supply of 50ML Ga. In the case of the sample with the 50ML of Ga, not Stranski-Krastanov (S-K) mode but a flat surface is observed after the crystallization and annealing process. However, without 50ML of Ga, the S-K mode occurs. Although photoluminescence spectra of these samples are observed at same wavelength around 950 nm, the FWHM of the PL spectrum with 50ML Ga (22meV) is narrower than that of without 50ML Ga (100meV), and the intensity of PL spectrum with 50ML of Ga is thirty times stronger than that of without 50ML Ga. These results indicate that the uniform InGa droplets changed into the uniform InGaAs QDs embedded in GaAs. Therefore, the SPEED is very useful fabrication method for the high quality InGaAs QDs. @FootnoteText@ @footnote 1@ N. Koguchi and K. Ishige, Jpn. J. Appl. Phys. 32, 2057 (1993).