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

Research output: Contribution to journal › Article › peer-review

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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.

Funding

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.

Funders	Funder number
Engineering and Physical Sciences Research Council	EP/E000673/1, 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.

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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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