Co-reporter:Takaaki Mano, Kazutaka Mitsuishi, Neul Ha, Akihiro Ohtake, Andrea Castellano, Stefano Sanguinetti, Takeshi Noda, Yoshiki Sakuma, Takashi Kuroda, and Kazuaki Sakoda
Crystal Growth & Design 2016 Volume 16(Issue 9) pp:5412-5417
Publication Date(Web):August 18, 2016
DOI:10.1021/acs.cgd.6b00899
We have successfully grown high quality InxGa1–xAs metamorphic layer on GaAs (111)A using molecular beam epitaxy. Inserting a thin 3.0–7.1 monolayer (ML) InAs interlayer between the In0.25Ga0.75As and GaAs allowed the formation of a nearly lattice-relaxed In0.25Ga0.75As with a very flat upper surface. However, when the thickness of the inserted InAs is thinner or thicker than these values, we observed degradation of crystal quality and/or surface morphology. We also revealed this technique to be applicable to the formation of a high quality metamorphic InxGa1–xAs layer with a range of In compositions (0.25 ≤ x ≤ 0.78) on GaAs (111)A. Cross-sectional scanning transmission electron microscope studies revealed that misfit dislocations formed only at the interface of InAs and GaAs, not at the interface of In0.25Ga0.75As and InAs. From the dislocation density analysis, it is suggested that the dislocation density was decreased by growing In0.25Ga0.75As on InAs, which effectively contribute the strain relaxation of In0.25Ga0.75As. The InGaAs/InAlAs quantum wells that were formed on the metamorphic layers exhibit clear photoluminescence emissions up to room temperature.
Co-reporter:T. Mano, K. Mitsuishi, Y. Nakayama, T. Noda, K. Sakoda
Applied Surface Science 2008 Volume 254(Issue 23) pp:7770-7773
Publication Date(Web):30 September 2008
DOI:10.1016/j.apsusc.2008.02.025
Abstract
We investigated detailed structural properties of GaAs nanostructures formed by a supply of intense As4 flux to Ga droplets. Scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM) revealed that whisker-like nanostructures had formed on the truncated cone-shaped bases after crystallization. Moreover, electron energy loss spectroscopy in scanning transmission electron microscopy (STEM-EELS) revealed that elemental Ga atoms remained inside the nanostructures while outside, some had crystallized into GaAs. These findings suggest that crystallization started at the edges of the droplets and the GaAs grew upward along the periphery of the droplets until the droplets were completely covered with crystallized GaAs.
Co-reporter:T. Mano, T. Noda, M. Yamagiwa, N. Koguchi
Thin Solid Films 2006 Volume 515(Issue 2) pp:531-534
Publication Date(Web):25 October 2006
DOI:10.1016/j.tsf.2005.12.289
We demonstrate self-assembly of GaAs double quantum dots (DQDs) by droplet epitaxy in a lattice-matched system in addition to concentric quantum double rings (CQDRs). The growth mechanism of these complex nanostructures is understood by taking into account the two crystallization processes; the counter-migration (of Ga and As atoms)-induced crystallization and droplet-edge-enhanced crystallization. By tuning the balance between these two processes, completely different types of the coupled quantum nanostructures are created.
Co-reporter:T. Mano, T. Kuroda, K. Mitsuishi, T. Noda, K. Sakoda
Journal of Crystal Growth (15 March 2009) Volume 311(Issue 7) pp:1828-1831
Publication Date(Web):15 March 2009
DOI:10.1016/j.jcrysgro.2008.11.043
We investigated the self-assembly of GaAs/AlGaAs quantum dots (QDs) on GaAs (3 1 1)A substrates by droplet epitaxy. High-density Ga droplets were formed on the (3 1 1)A surfaces due to the short surface migration distance of Ga atoms. The maximum area density exceeded 1011 /cm2. These Ga droplets were crystallized into dot-shaped nanostructures (QDs) even by the irradiation of low As4 flux intensity. The capped GaAs QDs exhibited efficient, narrow PL emission at 5 K, indicating their high quality and uniformity.
