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Fabrication of low-density GaN/AlN quantum dots via GaN thermal decomposition in MOCVD.

Zhang J, Li S, Xiong H, Tian W, Li Y, Fang Y, Wu Z, Dai J, Xu J, Li X, Chen C - Nanoscale Res Lett (2014)

Bottom Line: With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD).Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 10(8) cm(-2).X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China.

ABSTRACT
With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD). Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 10(8) cm(-2). X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN.

No MeSH data available.


XPS spectra of (a) Ga2p and (b) N1s for samples A, B, and C. The background lines and the fitted lines were also subtracted.
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Figure 4: XPS spectra of (a) Ga2p and (b) N1s for samples A, B, and C. The background lines and the fitted lines were also subtracted.

Mentions: As is shown in Figure 4, since XPS analysis was performed for samples A, B, and C, Ga2p and N1s core level spectra were measured. For both of the XPS spectra, the C1s peak at approximately 285.0 eV was used as binding-energy reference. Baselines were fixed using a Shirley background subtraction model and all peaks were fitted using a linear combination of 80% Gaussian and 20% Lorentzian line shapes. On the one hand, the Ga2p spectra are analyzed in Figure 4a. Both samples A and B have a Ga2p peak which can be fitted as only one subpeak located at 1,117.1 eV, which is assigned to Ga-N bond [22-24]. So there are no Ga droplets but GaN on the surface of samples A and B, indicating that the Ga desorption rate exceed the GaN decomposition rate. On the contrary, if the Ga desorption rate is less than the GaN decomposition rate, Ga droplets will generate in a chemical manner and Ga-Ga bond will be observed. No Ga2p peaks were observed in sample C, confirming that sample C is just the AlN buffer after H2 decomposition. On the other hand, the N1s spectra are analyzed in Figure 4b. For sample A, the N1s spectra can be decomposed into a total of four fitted subpeaks at 397.0, 398.7, and 400.3 eV, which were assigned to N-Ga bond, N-H2 bond and N-H3 bond [25,26], respectively. Only GaN existed on the surface of sample A. For sample C, the N1s spectra can be decomposed into one subpeaks at 398.7 eV, which is assigned to N-Al bond [27]. Only AlN existed on the surface of sample C. For sample B, the N1s spectra were decomposed into a total of four fitted subpeaks at 396.2, 397.0, 398.7, and 400.3 eV, which can be assigned to N-Al bond, N-Ga bond, N-H2 bond, and N-H3 bond, respectively. These fitted subpeaks coincide with the fitted subpeaks of samples A and C, providing a chemical evidence for the existence of GaN QDs formed on the AlN buffer. In addition, the N-H2 bond and N-H3 bond were obtained in samples A and B but did not exist in sample C, indicating that the appearance of N-H2 bond and N-H3 bond were caused by the interaction of decomposed GaN and hydrogen at high temperature.


Fabrication of low-density GaN/AlN quantum dots via GaN thermal decomposition in MOCVD.

Zhang J, Li S, Xiong H, Tian W, Li Y, Fang Y, Wu Z, Dai J, Xu J, Li X, Chen C - Nanoscale Res Lett (2014)

XPS spectra of (a) Ga2p and (b) N1s for samples A, B, and C. The background lines and the fitted lines were also subtracted.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128446&req=5

Figure 4: XPS spectra of (a) Ga2p and (b) N1s for samples A, B, and C. The background lines and the fitted lines were also subtracted.
Mentions: As is shown in Figure 4, since XPS analysis was performed for samples A, B, and C, Ga2p and N1s core level spectra were measured. For both of the XPS spectra, the C1s peak at approximately 285.0 eV was used as binding-energy reference. Baselines were fixed using a Shirley background subtraction model and all peaks were fitted using a linear combination of 80% Gaussian and 20% Lorentzian line shapes. On the one hand, the Ga2p spectra are analyzed in Figure 4a. Both samples A and B have a Ga2p peak which can be fitted as only one subpeak located at 1,117.1 eV, which is assigned to Ga-N bond [22-24]. So there are no Ga droplets but GaN on the surface of samples A and B, indicating that the Ga desorption rate exceed the GaN decomposition rate. On the contrary, if the Ga desorption rate is less than the GaN decomposition rate, Ga droplets will generate in a chemical manner and Ga-Ga bond will be observed. No Ga2p peaks were observed in sample C, confirming that sample C is just the AlN buffer after H2 decomposition. On the other hand, the N1s spectra are analyzed in Figure 4b. For sample A, the N1s spectra can be decomposed into a total of four fitted subpeaks at 397.0, 398.7, and 400.3 eV, which were assigned to N-Ga bond, N-H2 bond and N-H3 bond [25,26], respectively. Only GaN existed on the surface of sample A. For sample C, the N1s spectra can be decomposed into one subpeaks at 398.7 eV, which is assigned to N-Al bond [27]. Only AlN existed on the surface of sample C. For sample B, the N1s spectra were decomposed into a total of four fitted subpeaks at 396.2, 397.0, 398.7, and 400.3 eV, which can be assigned to N-Al bond, N-Ga bond, N-H2 bond, and N-H3 bond, respectively. These fitted subpeaks coincide with the fitted subpeaks of samples A and C, providing a chemical evidence for the existence of GaN QDs formed on the AlN buffer. In addition, the N-H2 bond and N-H3 bond were obtained in samples A and B but did not exist in sample C, indicating that the appearance of N-H2 bond and N-H3 bond were caused by the interaction of decomposed GaN and hydrogen at high temperature.

Bottom Line: With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD).Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 10(8) cm(-2).X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China.

ABSTRACT
With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD). Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 10(8) cm(-2). X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN.

No MeSH data available.