Fig. 6: Nanopatterned template for AlGaN/AlN epitaxial lateral overgrowth.

a Schematic diagram of silica nanosphere lithography. b, c SEM images of the nano-patterned substrate (NPS). d Cross-section and e plane-view SEM images of the ELO-AlN layer on the NPS. f AFM image shows the macro-steps on the AlN surface. Reprinted with permission from Donghyun et al.¹¹⁹. Copyright 2017 American Institute of Physics. g SEM cross-sectional image of ELO-AlN nanorod pattern with air gaps. h SEM image of ELO-AlN on sapphire. Reprinted with permission from Conroy et al.¹²¹. Copyright 2015 The Royal Society of Chemistry. i Coalesced AlGaN nanowire double heterostructure LED, the following two images are cross-sectional STM-HAADF image and high-magnification image, respectively. Reprinted with permission from Binh et al.¹²². Copyright 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim