skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Self-assembled GaN hexagonal micropyramid and microdisk

Abstract

The self-assembled GaN hexagonal micropyramid and microdisk were grown on LiAlO{sub 2} by plasma-assisted molecular-beam epitaxy. It was found that the (0001) disk was established with the capture of N atoms by most-outside Ga atoms as the (1x1) surface was constructing, while the pyramid was obtained due to the missing of most-outside N atoms. The intensity of cathode luminescence excited from the microdisk was one order of amplitude greater than that from M-plane GaN.

Authors:
; ; ; ;  [1]
  1. Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)
Publication Date:
OSTI Identifier:
21175956
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 94; Journal Issue: 6; Other Information: DOI: 10.1063/1.3079078; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CATHODES; CATHODOLUMINESCENCE; CRYSTAL GROWTH; GALLIUM NITRIDES; MOLECULAR BEAM EPITAXY; SEMICONDUCTOR MATERIALS

Citation Formats

Lo Ikai, Hsieh, C.-H., Hsu, Y.-C., Pang, W.-Y., and Chou, M.-C.. Self-assembled GaN hexagonal micropyramid and microdisk. United States: N. p., 2009. Web. doi:10.1063/1.3079078.
Lo Ikai, Hsieh, C.-H., Hsu, Y.-C., Pang, W.-Y., & Chou, M.-C.. Self-assembled GaN hexagonal micropyramid and microdisk. United States. doi:10.1063/1.3079078.
Lo Ikai, Hsieh, C.-H., Hsu, Y.-C., Pang, W.-Y., and Chou, M.-C.. Mon . "Self-assembled GaN hexagonal micropyramid and microdisk". United States. doi:10.1063/1.3079078.
@article{osti_21175956,
title = {Self-assembled GaN hexagonal micropyramid and microdisk},
author = {Lo Ikai and Hsieh, C.-H. and Hsu, Y.-C. and Pang, W.-Y. and Chou, M.-C.},
abstractNote = {The self-assembled GaN hexagonal micropyramid and microdisk were grown on LiAlO{sub 2} by plasma-assisted molecular-beam epitaxy. It was found that the (0001) disk was established with the capture of N atoms by most-outside Ga atoms as the (1x1) surface was constructing, while the pyramid was obtained due to the missing of most-outside N atoms. The intensity of cathode luminescence excited from the microdisk was one order of amplitude greater than that from M-plane GaN.},
doi = {10.1063/1.3079078},
journal = {Applied Physics Letters},
number = 6,
volume = 94,
place = {United States},
year = {Mon Feb 09 00:00:00 EST 2009},
month = {Mon Feb 09 00:00:00 EST 2009}
}
  • The authors have found the self-assembled formation of ZnO hexagonal micropyramids after the growth of a sufficiently thick ZnO layer on a (0001) Al{sub 2}O{sub 3} substrate by rf-magnetron sputtering deposition. It was confirmed by scanning electron microscopy that the orientations of the micropyramids are well arranged. The reflection and photoluminescence spectra at 10 K demonstrate that optical properties of the total growth layer are of high quality. The noticeable discovery with the use of cathodoluminescence spectroscopy is that the luminescence intensity of the micropyramids is 30 times stronger than that of the underlying layer; namely, strong enhancement of luminescencemore » is realized in the self-assembled micropyramids.« less
  • Molecular-beam epitaxy of In{sub x}Ga{sub 1-x}N alloy on GaN(0001) is investigated by scanning tunneling microscopy. The Stranski-Krastanov mode of growth of the alloy is followed, where the newly nucleated three-dimensional islands are initially coherent to the underlying GaN and the wetting layer, but then become dislocated when grown bigger than about 20 nm in the lateral dimension. Two types of islands show different shapes, where the coherent ones are cone shaped and the dislocated ones are pillar like, having flat-tops. Within a certain range of material coverage, the surface contains both coherent and dislocated islands, showing an overall bimodal island-sizemore » distribution. The continued deposition on such surfaces leads to the pronounced growth of dislocated islands, whereas the sizes of the coherent islands change very little.« less
  • Growth of YMnO{sub 3} on GaN (0001) using molecular beam epitaxy at temperatures greater than 850 deg. C resulted in the spontaneous formation of crystalline prisms, ranging from 20 to 60 nm in height and 50 to 500 nm in lateral size, surrounded by a 6 nm thick continuous YMnO{sub 3} film. The local dielectric properties were measured using scanning surface probe microscopy. The prisms were ferroelectric at room temperature and their ferroelectric properties were enhanced for taller prisms. This is consistent with these structures being less constrained than the continuous layer, which is clamped by the surrounding unpolarized film.
  • GaN quantum dots (QDs) grown in semipolar (1122) AlN by plasma-assisted molecular-beam epitaxy were studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy techniques. The embedded (1122)-grown QDs exhibited pyramidal or truncated-pyramidal morphology consistent with the symmetry of the nucleating plane, and were delimited by nonpolar and semipolar nanofacets. It was also found that, in addition to the (1122) surface, QDs nucleated at depressions comprising (1011) facets. This was justified by ab initio density functional theory calculations showing that such GaN/AlN facets are of lower energy compared to (1122). Based on quantitative high-resolution TEM strain measurements, the three-dimensionalmore » QD strain state was analyzed using finite-element simulations. The internal electrostatic field was then estimated, showing small potential drop along the growth direction, and limited localization at most QD interfaces.« less
  • Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy is studied through a combination of two in situ tools: grazing incidence x-ray diffraction and reflection high energy electron diffraction. Growth on bare Si(111) and on AlN/Si(111) is compared. A significantly larger delay at nucleation is observed for nanowires grown on bare Si(111). The difference in the nucleation delay is correlated to a dissimilarity of chemical reactivity between Al and Ga with nitrided Si(111).