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Characterisation of InGaN by Photoconductive Atomic Force Microscopy

Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
Author to whom correspondence should be addressed.
Materials 2018, 11(10), 1794;
Received: 5 July 2018 / Revised: 29 August 2018 / Accepted: 3 September 2018 / Published: 21 September 2018
(This article belongs to the Special Issue III-Nitrides Semiconductor Research in the UK and Ireland)
Nanoscale structure has a large effect on the optoelectronic properties of InGaN, a material vital for energy saving technologies such as light emitting diodes. Photoconductive atomic force microscopy (PC-AFM) provides a new way to investigate this effect. In this study, PC-AFM was used to characterise four thick (∼130 nm) In x Ga 1 x N films with x = 5%, 9%, 12%, and 15%. Lower photocurrent was observed on elevated ridges around defects (such as V-pits) in the films with x 12 %. Current-voltage curve analysis using the PC-AFM setup showed that this was due to a higher turn-on voltage on these ridges compared to surrounding material. To further understand this phenomenon, V-pit cross sections from the 9% and 15% films were characterised using transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. This identified a subsurface indium-deficient region surrounding the V-pit in the lower indium content film, which was not present in the 15% sample. Although this cannot directly explain the impact of ridges on turn-on voltage, it is likely to be related. Overall, the data presented here demonstrate the potential of PC-AFM in the field of III-nitride semiconductors. View Full-Text
Keywords: InGaN; photoconductive atomic force microscopy; dislocations InGaN; photoconductive atomic force microscopy; dislocations
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Weatherley, T.F.K.; Massabuau, F.C.-P.; Kappers, M.J.; Oliver, R.A. Characterisation of InGaN by Photoconductive Atomic Force Microscopy. Materials 2018, 11, 1794.

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