Defect reduction in GaN/(0001)sapphire films grown by molecular beam epitaxy using nanocolumn intermediate layers

D. Cherns; L. Meshi; I. Griffiths; S. Khongphetsak; S. V. Novikov; N. Farley; R. P. Campion; C. T. Foxon

doi:10.1063/1.2899944

Defect reduction in GaN/(0001)sapphire films grown by molecular beam epitaxy using nanocolumn intermediate layers

D. Cherns, L. Meshi, I. Griffiths, S. Khongphetsak, S. V. Novikov, N. Farley, R. P. Campion, C. T. Foxon

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Abstract

Transmission and scanning electron microscopies are used to examine the epitaxial lateral overgrowth of GaN on GaN nanocolumns grown on AlN/(0001)sapphire by molecular beam epitaxy. Initially, N-rich growth gave a bimodal morphology consisting of defect-free Ga-polar nanocolumns emanating from a compact, highly defective N-polar layer. Under subsequent Ga-rich conditions, the nanocolumns grew laterally to produce continuous Ga-polar overlayers. Threading dislocation (TD) densities in the overlayer were in the range of 108 - 109 cm-2, up to two orders of magnitude less than in the N-polar underlayer. It is proposed that the change in polarity is a key factor controlling the reduction in TD density.

Original language	English
Article number	121902
Journal	Applied Physics Letters
Volume	92
Issue number	12
DOIs	https://doi.org/10.1063/1.2899944
State	Published - 2008
Externally published	Yes

Bibliographical note

Funding Information:
The authors are grateful to the UK Engineering and Physical Sciences Research Council (EPSRC) for support for this work under Grant No. EP/D080762/1.

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10.1063/1.2899944

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abstract = "Transmission and scanning electron microscopies are used to examine the epitaxial lateral overgrowth of GaN on GaN nanocolumns grown on AlN/(0001)sapphire by molecular beam epitaxy. Initially, N-rich growth gave a bimodal morphology consisting of defect-free Ga-polar nanocolumns emanating from a compact, highly defective N-polar layer. Under subsequent Ga-rich conditions, the nanocolumns grew laterally to produce continuous Ga-polar overlayers. Threading dislocation (TD) densities in the overlayer were in the range of 108 - 109 cm-2, up to two orders of magnitude less than in the N-polar underlayer. It is proposed that the change in polarity is a key factor controlling the reduction in TD density.",

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AU - Cherns, D.

AU - Meshi, L.

AU - Griffiths, I.

AU - Khongphetsak, S.

AU - Novikov, S. V.

AU - Farley, N.

AU - Campion, R. P.

AU - Foxon, C. T.

N1 - Funding Information: The authors are grateful to the UK Engineering and Physical Sciences Research Council (EPSRC) for support for this work under Grant No. EP/D080762/1.

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AB - Transmission and scanning electron microscopies are used to examine the epitaxial lateral overgrowth of GaN on GaN nanocolumns grown on AlN/(0001)sapphire by molecular beam epitaxy. Initially, N-rich growth gave a bimodal morphology consisting of defect-free Ga-polar nanocolumns emanating from a compact, highly defective N-polar layer. Under subsequent Ga-rich conditions, the nanocolumns grew laterally to produce continuous Ga-polar overlayers. Threading dislocation (TD) densities in the overlayer were in the range of 108 - 109 cm-2, up to two orders of magnitude less than in the N-polar underlayer. It is proposed that the change in polarity is a key factor controlling the reduction in TD density.

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Defect reduction in GaN/(0001)sapphire films grown by molecular beam epitaxy using nanocolumn intermediate layers

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