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Patterned growth of InGaN/GaN quantum wells on freestanding GaN grating by molecular beam epitaxy.

Wang Y, Hu F, Hane K - Nanoscale Res Lett (2011)

Bottom Line: Importantly, coalescences between two side facets are realized to generate epitaxial gratings with triangular section.Thin epitaxial gratings produce the promising photoluminescence performance.This work provides a feasible way for further GaN-based integrated optics devices by a combination of GaN micromachining and epitaxial growth on a GaN-on-silicon substrate.PACS81.05.Ea; 81.65.Cf; 81.15.Hi.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nanomechanics, Tohoku University, Sendai 980-8579, Japan. wyjjy@yahoo.com.

ABSTRACT
We report here the epitaxial growth of InGaN/GaN quantum wells on freestanding GaN gratings by molecular beam epitaxy (MBE). Various GaN gratings are defined by electron beam lithography and realized on GaN-on-silicon substrate by fast atom beam etching. Silicon substrate beneath GaN grating region is removed from the backside to form freestanding GaN gratings, and the patterned growth is subsequently performed on the prepared GaN template by MBE. The selective growth takes place with the assistance of nanoscale GaN gratings and depends on the grating period P and the grating width W. Importantly, coalescences between two side facets are realized to generate epitaxial gratings with triangular section. Thin epitaxial gratings produce the promising photoluminescence performance. This work provides a feasible way for further GaN-based integrated optics devices by a combination of GaN micromachining and epitaxial growth on a GaN-on-silicon substrate.PACS81.05.Ea; 81.65.Cf; 81.15.Hi.

No MeSH data available.


Photoluminescence (PL) spectra of the resultant epitaxial gratings. (a) PL spectra of epitaxial films on unpatterned template; (b)-(e) PL spectra of the resultant epitaxial gratings: (b) 700-nm-period gratings; (c) 500-nm-period gratings; (d) 450-nm-period gratings; (e) 400-nm-period gratings.
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Figure 6: Photoluminescence (PL) spectra of the resultant epitaxial gratings. (a) PL spectra of epitaxial films on unpatterned template; (b)-(e) PL spectra of the resultant epitaxial gratings: (b) 700-nm-period gratings; (c) 500-nm-period gratings; (d) 450-nm-period gratings; (e) 400-nm-period gratings.

Mentions: The photoluminescence (PL) spectra of the resultant epitaxial gratings are measured at room temperature using a 325-nm He-Cd laser source. The PL of InGaN/GaN QWs deposited on unpatterned area is shown in Figure 6a. Since the silicon substrate is removed and the slab is thinned by wet etching, the PL intensity is greatly for freestanding InGaN/GaN QWs slab. Figure 6b shows the PL spectra of 700-nm-period epitaxial gratings with various grating widths. The PL peaks at approximately 436.4 nm are associated with the excitation of the InGaN/GaN QWs active layers. With decreasing grating width W from approximately 500 nm to approximately 250 nm, the PL peak and the integrated intensity are significantly increased, corresponding to the improvement in the selective growth. The PL spectra of 500-nm-period epitaxial gratings are shown in Figure 6c and demonstrate the similar optical performances. The PL peaks are about 436.4 nm, and the corresponding PL intensities are improved, indicating that small grating period is helpful for the patterned growth. However, the PL spectra illustrated in Figure 6e, f is different as the grating period decreases to 450 and 400 nm, where the number of GaN nanocolumns is gradually increased. Especially for the 400-nm-period epitaxial gratings, the PL peaks are about 436.4 nm, but the PL intensities are greatly improved with increasing the grating width from approximately 150 nm to approximately 250 nm. However, the PL from 200-nm grating width sample is stronger than it from 250-nm-grating width sample for the 450-nm-period epitaxial gratings. It might be explained by the formation of epitaxial nanocolumns. Both epitaxial grating and nanocolumns contribute to the PL excitation. The number of epitaxial nanocolumns is increased with increasing the grating width, whereas the epitaxial gratings with smooth facets are easily formed with decreasing the grating width. Hence, the epitaxial structures generated in reality determine which one plays the dominant influence on the PL spectra. On the other hand, thin InGaN/GaN QWs layers are incorporated in the upper part of the epitaxial gratings, the film structures beneath smooth side facets are rough, and the scattering losses are thus very large. Consequently, there is no clear signal to reflect the interaction between the excited light and the grating structures.


Patterned growth of InGaN/GaN quantum wells on freestanding GaN grating by molecular beam epitaxy.

Wang Y, Hu F, Hane K - Nanoscale Res Lett (2011)

Photoluminescence (PL) spectra of the resultant epitaxial gratings. (a) PL spectra of epitaxial films on unpatterned template; (b)-(e) PL spectra of the resultant epitaxial gratings: (b) 700-nm-period gratings; (c) 500-nm-period gratings; (d) 450-nm-period gratings; (e) 400-nm-period gratings.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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Figure 6: Photoluminescence (PL) spectra of the resultant epitaxial gratings. (a) PL spectra of epitaxial films on unpatterned template; (b)-(e) PL spectra of the resultant epitaxial gratings: (b) 700-nm-period gratings; (c) 500-nm-period gratings; (d) 450-nm-period gratings; (e) 400-nm-period gratings.
Mentions: The photoluminescence (PL) spectra of the resultant epitaxial gratings are measured at room temperature using a 325-nm He-Cd laser source. The PL of InGaN/GaN QWs deposited on unpatterned area is shown in Figure 6a. Since the silicon substrate is removed and the slab is thinned by wet etching, the PL intensity is greatly for freestanding InGaN/GaN QWs slab. Figure 6b shows the PL spectra of 700-nm-period epitaxial gratings with various grating widths. The PL peaks at approximately 436.4 nm are associated with the excitation of the InGaN/GaN QWs active layers. With decreasing grating width W from approximately 500 nm to approximately 250 nm, the PL peak and the integrated intensity are significantly increased, corresponding to the improvement in the selective growth. The PL spectra of 500-nm-period epitaxial gratings are shown in Figure 6c and demonstrate the similar optical performances. The PL peaks are about 436.4 nm, and the corresponding PL intensities are improved, indicating that small grating period is helpful for the patterned growth. However, the PL spectra illustrated in Figure 6e, f is different as the grating period decreases to 450 and 400 nm, where the number of GaN nanocolumns is gradually increased. Especially for the 400-nm-period epitaxial gratings, the PL peaks are about 436.4 nm, but the PL intensities are greatly improved with increasing the grating width from approximately 150 nm to approximately 250 nm. However, the PL from 200-nm grating width sample is stronger than it from 250-nm-grating width sample for the 450-nm-period epitaxial gratings. It might be explained by the formation of epitaxial nanocolumns. Both epitaxial grating and nanocolumns contribute to the PL excitation. The number of epitaxial nanocolumns is increased with increasing the grating width, whereas the epitaxial gratings with smooth facets are easily formed with decreasing the grating width. Hence, the epitaxial structures generated in reality determine which one plays the dominant influence on the PL spectra. On the other hand, thin InGaN/GaN QWs layers are incorporated in the upper part of the epitaxial gratings, the film structures beneath smooth side facets are rough, and the scattering losses are thus very large. Consequently, there is no clear signal to reflect the interaction between the excited light and the grating structures.

Bottom Line: Importantly, coalescences between two side facets are realized to generate epitaxial gratings with triangular section.Thin epitaxial gratings produce the promising photoluminescence performance.This work provides a feasible way for further GaN-based integrated optics devices by a combination of GaN micromachining and epitaxial growth on a GaN-on-silicon substrate.PACS81.05.Ea; 81.65.Cf; 81.15.Hi.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nanomechanics, Tohoku University, Sendai 980-8579, Japan. wyjjy@yahoo.com.

ABSTRACT
We report here the epitaxial growth of InGaN/GaN quantum wells on freestanding GaN gratings by molecular beam epitaxy (MBE). Various GaN gratings are defined by electron beam lithography and realized on GaN-on-silicon substrate by fast atom beam etching. Silicon substrate beneath GaN grating region is removed from the backside to form freestanding GaN gratings, and the patterned growth is subsequently performed on the prepared GaN template by MBE. The selective growth takes place with the assistance of nanoscale GaN gratings and depends on the grating period P and the grating width W. Importantly, coalescences between two side facets are realized to generate epitaxial gratings with triangular section. Thin epitaxial gratings produce the promising photoluminescence performance. This work provides a feasible way for further GaN-based integrated optics devices by a combination of GaN micromachining and epitaxial growth on a GaN-on-silicon substrate.PACS81.05.Ea; 81.65.Cf; 81.15.Hi.

No MeSH data available.