Defect reduction in GaN/(0001)sapphire films grown by molecular beam epitaxy using nanocolumn intermediate layers
- Department of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)
- Department of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
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 10{sup 8}-10{sup 9} cm{sup -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.
- OSTI ID:
- 21120623
- Journal Information:
- Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 12 Vol. 92; ISSN APPLAB; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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