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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

XRD of the GaN NWs grown using 10% H2 with peaks corresponding to the (100), (002), (101) crystallographic planes of the hexagonal wurtzite structure of GaN. The inset shows RT PL with a peak at 3.42 eV (≡362 nm).
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Figure 2: XRD of the GaN NWs grown using 10% H2 with peaks corresponding to the (100), (002), (101) crystallographic planes of the hexagonal wurtzite structure of GaN. The inset shows RT PL with a peak at 3.42 eV (≡362 nm).

Mentions: GaN NWs were successfully grown on 0.7 nm Au/Si(001) via the direct reaction of Ga with NH3 at 900°C under a flow of 20 sccm NH3 and 90 sccm N2:10 sccm H2. The GaN NWs shown in Figure 1a had diameters of 50 nm and lengths up to 2 μm, confirming that Au does not inhibit their growth. More importantly, the GaN NWs are straight in agreement with the findings of Hou and Hong [12] who obtained long and bent GaN NWs using N and Ar and straight GaN NWs by adding only a few % H2. The GaN NWs grown using 10% H2 exhibited clear peaks in the XRD as shown in Figure 2 corresponding to GaN with a hexagonal wurtzite structure and lattice constants of a = 0.318 nm and c = 0.518 nm [10]. Excitation of the GaN NWs shown in Figure 1a using λ = 290 nm resulted in strong RT PL shown in the inset of Figure 2, where the prominent peak corresponds to band edge emission of GaN at 3.42 eV. Note that there was very little PL around 540 nm commonly referred to as the "yellow luminescence" band of GaN. Despite the improvement in the shape of the GaN NWs obtained with 10% H2 we found that the uniformity was poor over the Au/Si(001) surface due to the high boiling point of Ga, i.e., 1983°C and the resultant low vapor pressure at 900°C. The uniformity was improved significantly by fragmenting the Ga thereby increasing the vapor pressure, but this inadvertently led to the formation of connected crystallites or an α-like GaN layer.


Gallium hydride vapor phase epitaxy of GaN nanowires.

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

XRD of the GaN NWs grown using 10% H2 with peaks corresponding to the (100), (002), (101) crystallographic planes of the hexagonal wurtzite structure of GaN. The inset shows RT PL with a peak at 3.42 eV (≡362 nm).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: XRD of the GaN NWs grown using 10% H2 with peaks corresponding to the (100), (002), (101) crystallographic planes of the hexagonal wurtzite structure of GaN. The inset shows RT PL with a peak at 3.42 eV (≡362 nm).
Mentions: GaN NWs were successfully grown on 0.7 nm Au/Si(001) via the direct reaction of Ga with NH3 at 900°C under a flow of 20 sccm NH3 and 90 sccm N2:10 sccm H2. The GaN NWs shown in Figure 1a had diameters of 50 nm and lengths up to 2 μm, confirming that Au does not inhibit their growth. More importantly, the GaN NWs are straight in agreement with the findings of Hou and Hong [12] who obtained long and bent GaN NWs using N and Ar and straight GaN NWs by adding only a few % H2. The GaN NWs grown using 10% H2 exhibited clear peaks in the XRD as shown in Figure 2 corresponding to GaN with a hexagonal wurtzite structure and lattice constants of a = 0.318 nm and c = 0.518 nm [10]. Excitation of the GaN NWs shown in Figure 1a using λ = 290 nm resulted in strong RT PL shown in the inset of Figure 2, where the prominent peak corresponds to band edge emission of GaN at 3.42 eV. Note that there was very little PL around 540 nm commonly referred to as the "yellow luminescence" band of GaN. Despite the improvement in the shape of the GaN NWs obtained with 10% H2 we found that the uniformity was poor over the Au/Si(001) surface due to the high boiling point of Ga, i.e., 1983°C and the resultant low vapor pressure at 900°C. The uniformity was improved significantly by fragmenting the Ga thereby increasing the vapor pressure, but this inadvertently led to the formation of connected crystallites or an α-like GaN layer.

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