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      Wafer-scale selective area growth of GaN hexagonal prismatic nanostructures on c-sapphire substrate

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          Abstract

          Selective area growth of GaN nanostructures has been performed on full 2" c-sapphire substrates using Si3N4 mask patterned by nanoimprint lithography (array of 400 nm diameter circular holes). A new process has been developed to improve the homogeneity of the nucleation selectivity of c-oriented hexagonal prismatic nanostructures at high temperature (1040\circ C). It consists of an initial GaN nucleation step at 950 \circ C followed by ammonia annealing before high temperature growth. Structural analyses show that GaN nanostructures are grown in epitaxy with c-sapphire with lateral overgrowths on the mask. Strain and dislocations are observed at the interface due to the large GaN/sapphire lattice mismatch in contrast with the high quality of the relaxed crystals in the lateral overgrowth area. A cathodoluminescence study as a function of the GaN nanostructure size confirms these observations: the lateral overgrowth of GaN nanostructures has a low defect density and exhibits a stronger near band edge (NBE) emission than the crystal in direct epitaxy with sapphire. The shift of the NBE positions versus nanostructure size can be mainly attributed to a combination of compressive strain and silicon doping coming from surface mask diffusion.

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          Journal
          21 June 2011
          Article
          10.1016/j.jcrysgro.2011.03.007
          1106.4290
          be00b579-b6ce-4689-840c-94dc61bd988f

          http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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          Custom metadata
          Journal of Crystal Growth 322, 1 (2011) 15
          cond-mat.mtrl-sci
          ccsd

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