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Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy.

Wu P, Funato M, Kawakami Y - Sci Rep (2015)

Bottom Line: Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas.This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation.Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan.

ABSTRACT
Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0 eV (207 nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000 °C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 μm/h at 1550 °C using argon as the source transfer via the simple reaction Al + 1/2N2 → AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

No MeSH data available.


Related in: MedlinePlus

Crystallographic properties of 18-μm-thick AlN assessed by XRD.(a) Plot of FWHMs of the ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes as functions of the V/III ratio. (b) 2θ/ω profile of the symmetric plane. Single peak of AlN(0002) indicates [0001]-oriented growth of wurtzite AlN. (c) ϕ-scans of the asymmetric AlN and sapphire {102} planes. Six-fold symmetry of AlN indicates that AlN is a single-phase crystal. Disagreement between the AlN and sapphire peaks indicate an in-plane rotation by 30° to minimize the lattice mismatch. (d) ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes. Line widths at the half maximum are as narrow as 290 and 291 arcsec, respectively.
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f4: Crystallographic properties of 18-μm-thick AlN assessed by XRD.(a) Plot of FWHMs of the ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes as functions of the V/III ratio. (b) 2θ/ω profile of the symmetric plane. Single peak of AlN(0002) indicates [0001]-oriented growth of wurtzite AlN. (c) ϕ-scans of the asymmetric AlN and sapphire {102} planes. Six-fold symmetry of AlN indicates that AlN is a single-phase crystal. Disagreement between the AlN and sapphire peaks indicate an in-plane rotation by 30° to minimize the lattice mismatch. (d) ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes. Line widths at the half maximum are as narrow as 290 and 291 arcsec, respectively.

Mentions: The crystallinity of the grown AlN layers was assessed by XRD measurements. Figure 4a shows the full widths at half maximum (FWHMs) of the ω-scan of the AlN symmetric (0002) and asymmetric (102) diffractions as functions of the V/III ratio during growth. Although the variation due to the V/III ratio is insignificant, the narrowest widths are obtained with V/III~2200. In addition, V/III~2200 provides the fastest growth rate in this study (Fig. 3a), confirming that it is the best growth condition. Therefore, the results for the 18-μm-thick AlN layer on sapphire(0001) grown with V/III~2200 are used below as a representative material. Figure 4b shows the symmetric 2θ/ω profile. Apart from sapphire(0006), only the AlN(0002) diffraction is detected, indicating that the AlN layer is a [0001]-oriented wurtzite crystal. The crystallographic orientation in the (0001) plane is examined with ϕ scans of the AlN and sapphire asymmetric {102} planes (Fig. 4c). The clear six-fold symmetry observed for AlN indicates that AlN has a single-phase hexagonal wurtzite structure exclusive of other rotation domains. The angular difference between the AlN and sapphire diffractions is 30° due to the in-plane 30° rotation to mitigate the lattice mismatch, which is often reported for MOVPE or MBE nitride semiconductors on sapphire(0001)3036. (The three-fold symmetry of sapphire originates from the crystal structure of trigonal corundum.)


Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy.

Wu P, Funato M, Kawakami Y - Sci Rep (2015)

Crystallographic properties of 18-μm-thick AlN assessed by XRD.(a) Plot of FWHMs of the ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes as functions of the V/III ratio. (b) 2θ/ω profile of the symmetric plane. Single peak of AlN(0002) indicates [0001]-oriented growth of wurtzite AlN. (c) ϕ-scans of the asymmetric AlN and sapphire {102} planes. Six-fold symmetry of AlN indicates that AlN is a single-phase crystal. Disagreement between the AlN and sapphire peaks indicate an in-plane rotation by 30° to minimize the lattice mismatch. (d) ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes. Line widths at the half maximum are as narrow as 290 and 291 arcsec, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663762&req=5

f4: Crystallographic properties of 18-μm-thick AlN assessed by XRD.(a) Plot of FWHMs of the ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes as functions of the V/III ratio. (b) 2θ/ω profile of the symmetric plane. Single peak of AlN(0002) indicates [0001]-oriented growth of wurtzite AlN. (c) ϕ-scans of the asymmetric AlN and sapphire {102} planes. Six-fold symmetry of AlN indicates that AlN is a single-phase crystal. Disagreement between the AlN and sapphire peaks indicate an in-plane rotation by 30° to minimize the lattice mismatch. (d) ω-scan of the AlN symmetric (0002) and the asymmetric (102) planes. Line widths at the half maximum are as narrow as 290 and 291 arcsec, respectively.
Mentions: The crystallinity of the grown AlN layers was assessed by XRD measurements. Figure 4a shows the full widths at half maximum (FWHMs) of the ω-scan of the AlN symmetric (0002) and asymmetric (102) diffractions as functions of the V/III ratio during growth. Although the variation due to the V/III ratio is insignificant, the narrowest widths are obtained with V/III~2200. In addition, V/III~2200 provides the fastest growth rate in this study (Fig. 3a), confirming that it is the best growth condition. Therefore, the results for the 18-μm-thick AlN layer on sapphire(0001) grown with V/III~2200 are used below as a representative material. Figure 4b shows the symmetric 2θ/ω profile. Apart from sapphire(0006), only the AlN(0002) diffraction is detected, indicating that the AlN layer is a [0001]-oriented wurtzite crystal. The crystallographic orientation in the (0001) plane is examined with ϕ scans of the AlN and sapphire asymmetric {102} planes (Fig. 4c). The clear six-fold symmetry observed for AlN indicates that AlN has a single-phase hexagonal wurtzite structure exclusive of other rotation domains. The angular difference between the AlN and sapphire diffractions is 30° due to the in-plane 30° rotation to mitigate the lattice mismatch, which is often reported for MOVPE or MBE nitride semiconductors on sapphire(0001)3036. (The three-fold symmetry of sapphire originates from the crystal structure of trigonal corundum.)

Bottom Line: Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas.This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation.Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan.

ABSTRACT
Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0 eV (207 nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000 °C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 μm/h at 1550 °C using argon as the source transfer via the simple reaction Al + 1/2N2 → AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

No MeSH data available.


Related in: MedlinePlus