1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Mechanism of GaN quantum dot overgrowth by Al0.5Ga0.5N: Strain evolution and phase separation
Rent:
Rent this article for
USD
10.1063/1.4704682
/content/aip/journal/jap/111/8/10.1063/1.4704682
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/8/10.1063/1.4704682
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Typical AFM images of uncapped GaN QDs (a) and QDs capped with 2 ML (b), 12 ML (c), and 24 ML (d) thick Al0.5Ga0.5N layer.

Image of FIG. 2.
FIG. 2.

STEM-HAADF (a), (c), (d) and TEM (b) images of GaN QDs covered with 2 (a), 8 (b), 12 (c), and 24 (d) ML thick Al0.5Ga0.5N layer. In Z-contrast images GaN QDs appear with a bright contrast in comparison to the Al0.5Ga0.5N background, whereas Al-rich zones in (c) and (d) appear with a dark contrast. In the TEM image (b), GaN QDs appear dark because of the mass contrast. In (b) the positions occupied by the Al0.5Ga0.5N capping layer are shown by the white arrows.

Image of FIG. 3.
FIG. 3.

STEM-HAADF image of a part of GaN QD covered with 12 ML of Al0.5Ga0.5N (a). The white lines show profiles traced perpendicularly to the (0001) (b) and (1–103) (c) facets.

Image of FIG. 4.
FIG. 4.

HRTEM image of two neighbouring QDs (a) and corresponding ɛzz (b) and ɛxx (c) strain maps obtained using GPA. The inset in (a) shows a magnified HRTEM image pattern. The strain maps (b) and (c) were calculated with a Gaussian mask of size g/2 and normalised to the lattice parameter of Al0.5Ga0.5N. The white line in (b) displays the position of the strain profile shown in (d). The black lines in (c) show the QD contours determined from the ɛzz strain map.

Image of FIG. 5.
FIG. 5.

HRTEM image of two neighbouring QDs taken in the two-beam conditions (a). The corresponding ɛzz strain map (b) was obtained using Gaussian mask of size g/2. Arrows indicate zones of the phase separation. The inset is an enlargement of HRTEM image showing (0002) lattice fringes.

Image of FIG. 6.
FIG. 6.

ɛzz (a) and ɛxx (b) GPA strain maps of two surface QDs. The strain maps were calculated with a Gaussian mask of size g/4 and normalised to the lattice parameter of Al0.5Ga0.5N. The white line in (b) shows the position of the profile presented in (c).

Image of FIG. 7.
FIG. 7.

ɛzz (a) and ɛxx (b) GPA strain maps of QD covered with 12 ML of Al0.5Ga0.5N. The strain maps were calculated in the same way as in Fig. 6. The white line in (a) displays the position of the profile shown in (c). The black lines in (b) show the QD contours determined from the ɛzz strain map.

Image of FIG. 8.
FIG. 8.

Theoretically calculated distributions of ɛzz (a) and ɛxx (b) strain around a buried QD. The strain is given in percents relative to the lattice parameters of Al0.5Ga0.5N.

Image of FIG. 9.
FIG. 9.

Theoretically calculated distributions of ɛzz (a) and ɛxx (b) strain inside a surface QD. The strain is given in percents relative to the lattice parameter of Al0.5Ga0.5N.

Image of FIG. 10.
FIG. 10.

Theoretically calculated distributions of ɛzz (a) and ɛxx (b) strain around a QD capped with 12 ML of Al0.5Ga0.5N. The strain is given in percents relative to the lattice parameter of Al0.5Ga0.5N.

Image of FIG. 11.
FIG. 11.

Elastic energy density (eV/nm3) for a QD capped by 24 ML thick Al0.5Ga0.5N layer with homogeneous (a) and inhomogeneous (b) composition.

Image of FIG. 12.
FIG. 12.

Dynamics of the phase separation process in the Al0.5Ga0.5N capping layer. The GaN QDs and the wetting layer are in red, Al0.5Ga0.5N is in light brown, the Al-rich zones are in green and the Ga-rich zones are in red. The blue line shows the surface of the Al0.5Ga0.5N layer.

Image of FIG. 13.
FIG. 13.

Scheme of the strain distribution in the Al0.5Ga0.5N layer surrounding a GaN QD. The anion rows are withdrawn, the green points represent Al0.5/Ga0.5 rows, the orange ones represent Ga rows, the blue and the red ones represent, respectively, Al-rich and Ga-rich atomic rows. The purple dash lines show an area where the Al0.5Ga0.5N lattice is under tensile strain.

Loading

Article metrics loading...

/content/aip/journal/jap/111/8/10.1063/1.4704682
2012-04-19
2014-04-23
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Mechanism of GaN quantum dot overgrowth by Al0.5Ga0.5N: Strain evolution and phase separation
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/8/10.1063/1.4704682
10.1063/1.4704682
SEARCH_EXPAND_ITEM