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Phase separation in GaN/AlGaN quantum dots
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View: Figures


Image of FIG. 1.
FIG. 1.

ADF image of GaN/AlGaN QDs with the illumination angle of 15 mrad and the collection angle beyond 20 mrad. The three GaN QDs layers separated by an AlGaN spacer are clearly visible at the top part of the figure. At the bottom part, a stack of AlGaN , AlN (100 nm), and GaN (30 nm) buffer layers are shown.

Image of FIG. 2.
FIG. 2.

HAADF image of GaN QDs embedded in an matrix with the collection angle greater than 70 mrad. GaN QDs appear brighter with a truncated-pyramidal form. Note that the dark contrast above the QD is strongly related with the atomic number indicating the presence of an Al-rich zone.

Image of FIG. 3.
FIG. 3.

(a) Low-loss EELS spectra presenting the volume-plasmon peaks recorded at four different regions as shown in the HAADF image in the bottom-left inset (scale-bar equals to 5 nm). For comparison, the upper-left inset exhibits reference spectra recorded from GaN, AlN, and buffer layers. (b) Plasmon energy profile as a function of the probe position along a line-scan taken across the area shown in bottom-left inset of [Fig. 3(a)]. Spectra 1 to 4 were extracted from this line scan. The profile clearly demonstrates that AlGaN composition returns to its nominal stoichiometry away from the fluctuation zone. The upper-right inset in [Fig. 3(b)] exhibits as a function Al content extracted from values reported in the upper-left inset of [Fig. 3(a)]. This suggests that spectrum 3, with , corresponds to an Al content around 70%. All extracted values have an error of about ±0.05 eV.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Phase separation in GaN/AlGaN quantum dots