Abstract
AbstractThe nanoscale patterned sapphire substrates (NPSS) were prepared combining nanoimprint lithography and dry/wet etching technology. The NPSS was patterned with 300 nm diameter, 330 nm depth, 550 nm periodicity hexagonal close packed pillars. Coalescence of GaN has been achieved on the NPSS using MOVPE. The growth mode and conditions were discussed in detail, which was different from that of GaN epitaxial on planar sapphire. The AFM images showed the GaN on NPSS had a smoother surface, and the XRD results showed that the crystal quality had been improved by the NPSS. The threading dislocation density (TDD) suppression was observed in transmission electron microscopy. Depth‐resolved CL measurements were used to quantify the redshift in terms of bandgap renormalization and strain effects. It was supposed that the compressive stress in the GaN layers was changed gradually towards the growth surface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Published Version
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