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Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography.

Liu G, Zhao H, Zhang J, Park JH, Mawst LJ, Tansu N - Nanoscale Res Lett (2011)

Bottom Line: The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution.The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm.The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Optical Technologies, Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA 18015, USA. gul308@lehigh.edu.

ABSTRACT
Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.

No MeSH data available.


Schematic of two groups of QD samples with the structures of: (A) 1.5-nm InGaN sandwiched between 1 GaN layers (Sample A); (B) 3 nm InGaN sandwiched between 2-nm GaN layers (Sample B).
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Figure 2: Schematic of two groups of QD samples with the structures of: (A) 1.5-nm InGaN sandwiched between 1 GaN layers (Sample A); (B) 3 nm InGaN sandwiched between 2-nm GaN layers (Sample B).

Mentions: Both the n-GaN template and InGaN QD samples used in this study were grown by a vertical-type VEECO P-75 MOCVD reactor. The growths of the InGaN QD-active region and GaN barrier layers employed triethylgallium, trimethylindium, and ammonia (NH3) as gallium, indium, and nitrogen precursors, respectively. The use of trimethlygallium was employed for the growth of n-GaN template (Tg = 1080°C). The growth rates for InGaN active and GaN barrier layers in planar region were 3 and 2.4 nm/min, respectively. The growth temperature and growth pressure for the InGaN QDs and GaN barrier layers were kept at 735°C and 200 Torr, respectively. The top GaN barrier layer also serves as the cap layer for the sample, and its similar growth temperature with that of the InGaN QDs leads to minimal dissolution of the In during the barrier layer growth. The V/III molar ratios employed for the growths of the GaN templates, GaN barrier and InGaN active layers were 3900, 34500, and 18500, respectively. Based on growth calibration using XRD measurements, the In-content of the InGaN layer employed in the studies was calibrated as 15%. In our experiments, two sets of structures were investigated as shown in Figure 2, as follows: (1) Sample A consists of 1.5 nm InGaN layer sandwiched between GaN barrier layers each of 1 nm in the opening region with a total thickness designed to be 3.5 nm; and (2) Sample B consists of 3 nm InGaN layer sandwiched between GaN barrier layers of 2 nm each making the total thickness of 7 nm.


Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography.

Liu G, Zhao H, Zhang J, Park JH, Mawst LJ, Tansu N - Nanoscale Res Lett (2011)

Schematic of two groups of QD samples with the structures of: (A) 1.5-nm InGaN sandwiched between 1 GaN layers (Sample A); (B) 3 nm InGaN sandwiched between 2-nm GaN layers (Sample B).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211431&req=5

Figure 2: Schematic of two groups of QD samples with the structures of: (A) 1.5-nm InGaN sandwiched between 1 GaN layers (Sample A); (B) 3 nm InGaN sandwiched between 2-nm GaN layers (Sample B).
Mentions: Both the n-GaN template and InGaN QD samples used in this study were grown by a vertical-type VEECO P-75 MOCVD reactor. The growths of the InGaN QD-active region and GaN barrier layers employed triethylgallium, trimethylindium, and ammonia (NH3) as gallium, indium, and nitrogen precursors, respectively. The use of trimethlygallium was employed for the growth of n-GaN template (Tg = 1080°C). The growth rates for InGaN active and GaN barrier layers in planar region were 3 and 2.4 nm/min, respectively. The growth temperature and growth pressure for the InGaN QDs and GaN barrier layers were kept at 735°C and 200 Torr, respectively. The top GaN barrier layer also serves as the cap layer for the sample, and its similar growth temperature with that of the InGaN QDs leads to minimal dissolution of the In during the barrier layer growth. The V/III molar ratios employed for the growths of the GaN templates, GaN barrier and InGaN active layers were 3900, 34500, and 18500, respectively. Based on growth calibration using XRD measurements, the In-content of the InGaN layer employed in the studies was calibrated as 15%. In our experiments, two sets of structures were investigated as shown in Figure 2, as follows: (1) Sample A consists of 1.5 nm InGaN layer sandwiched between GaN barrier layers each of 1 nm in the opening region with a total thickness designed to be 3.5 nm; and (2) Sample B consists of 3 nm InGaN layer sandwiched between GaN barrier layers of 2 nm each making the total thickness of 7 nm.

Bottom Line: The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution.The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm.The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Optical Technologies, Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA 18015, USA. gul308@lehigh.edu.

ABSTRACT
Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.

No MeSH data available.