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Gallium hydride vapor phase epitaxy of GaN nanowires.

Zervos M, Othonos A - Nanoscale Res Lett (2011)

Bottom Line: The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001).The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs.Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanostructured Materials and Devices Laboratory, Department of Mechanical Engineering, Materials Science Group, School of Engineering, University of Cyprus, P,O, Box 20537, Nicosia 1678, Cyprus. zervos@ucy.ac.cy.

ABSTRACT
Straight GaN nanowires (NWs) with diameters of 50 nm, lengths up to 10 μm and a hexagonal wurtzite crystal structure have been grown at 900°C on 0.5 nm Au/Si(001) via the reaction of Ga with NH3 and N2:H2, where the H2 content was varied between 10 and 100%. The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001). Increasing the H2 content leads to an increase in the growth rate, a reduction in the areal density of the GaN NWs and a suppression of the underlying amorphous (α)-like GaN layer which occurs without H2. The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs. Moreover, the reduction in the areal density of the GaN NWs and suppression of the α-like GaN layer is attributed to the reaction of H2 with Ga in the immediate vicinity of the Au NPs. Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

No MeSH data available.


Related in: MedlinePlus

SEM image of GaN NWs obtained using 10% H2 (a) and 100% H2 (b) The inset in (a) shows the α-like GaN layer obtained with no H2, while the inset in (b) shows Au NPs obtained by heating 10 nm Au/Si(001) at 900°C using 100% H2. The Au NPs do not coalesce into larger clusters but remain isolated.
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Figure 1: SEM image of GaN NWs obtained using 10% H2 (a) and 100% H2 (b) The inset in (a) shows the α-like GaN layer obtained with no H2, while the inset in (b) shows Au NPs obtained by heating 10 nm Au/Si(001) at 900°C using 100% H2. The Au NPs do not coalesce into larger clusters but remain isolated.

Mentions: As described in detail elsewhere the direct reaction of Ga with NH3 using Ar as a carrier gas at 900°C leads to the growth of a few bent GaN NWs on top of an α-like GaN layer [10]. Such an α-like GaN layer, shown in the inset of Figure 1a, was obtained on 0.7 nm Au/Si(001) via the reaction of Ga and NH3 using Ar, under Ga-rich conditions at 10-1 mBar. The α-like GaN layer is irregular and consists of connected crystallites that have sizes of ≈ 500 nm. It is important to point out that a low yield, non-uniform distribution of bent GaN NWs was obtained on top of this α-like GaN layer which was readily and clearly observed by SEM. On the contrary, no deposition took place on plain Si(001) in accordance with the findings of Hou and Hong [12] who found GaN NWs on patterned Au but not on plain Si in between the Au.


Gallium hydride vapor phase epitaxy of GaN nanowires.

Zervos M, Othonos A - Nanoscale Res Lett (2011)

SEM image of GaN NWs obtained using 10% H2 (a) and 100% H2 (b) The inset in (a) shows the α-like GaN layer obtained with no H2, while the inset in (b) shows Au NPs obtained by heating 10 nm Au/Si(001) at 900°C using 100% H2. The Au NPs do not coalesce into larger clusters but remain isolated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211325&req=5

Figure 1: SEM image of GaN NWs obtained using 10% H2 (a) and 100% H2 (b) The inset in (a) shows the α-like GaN layer obtained with no H2, while the inset in (b) shows Au NPs obtained by heating 10 nm Au/Si(001) at 900°C using 100% H2. The Au NPs do not coalesce into larger clusters but remain isolated.
Mentions: As described in detail elsewhere the direct reaction of Ga with NH3 using Ar as a carrier gas at 900°C leads to the growth of a few bent GaN NWs on top of an α-like GaN layer [10]. Such an α-like GaN layer, shown in the inset of Figure 1a, was obtained on 0.7 nm Au/Si(001) via the reaction of Ga and NH3 using Ar, under Ga-rich conditions at 10-1 mBar. The α-like GaN layer is irregular and consists of connected crystallites that have sizes of ≈ 500 nm. It is important to point out that a low yield, non-uniform distribution of bent GaN NWs was obtained on top of this α-like GaN layer which was readily and clearly observed by SEM. On the contrary, no deposition took place on plain Si(001) in accordance with the findings of Hou and Hong [12] who found GaN NWs on patterned Au but not on plain Si in between the Au.

Bottom Line: The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001).The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs.Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanostructured Materials and Devices Laboratory, Department of Mechanical Engineering, Materials Science Group, School of Engineering, University of Cyprus, P,O, Box 20537, Nicosia 1678, Cyprus. zervos@ucy.ac.cy.

ABSTRACT
Straight GaN nanowires (NWs) with diameters of 50 nm, lengths up to 10 μm and a hexagonal wurtzite crystal structure have been grown at 900°C on 0.5 nm Au/Si(001) via the reaction of Ga with NH3 and N2:H2, where the H2 content was varied between 10 and 100%. The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001). Increasing the H2 content leads to an increase in the growth rate, a reduction in the areal density of the GaN NWs and a suppression of the underlying amorphous (α)-like GaN layer which occurs without H2. The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs. Moreover, the reduction in the areal density of the GaN NWs and suppression of the α-like GaN layer is attributed to the reaction of H2 with Ga in the immediate vicinity of the Au NPs. Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

No MeSH data available.


Related in: MedlinePlus