Gallium nitride(GaN)thin film of the nitrogen polarity(N-polar)was grown on C-plane sapphire and misoriented C-plane sapphire substrates respectively by metal-organic chemical vapor deposition(MOCVD).The misorientation angle is off-axis from C-plane toward M-plane of the substrates,and the angle is 2° and 4° respectively.The nitrogen polarity was confirmed by examining the images of the scanning electron microscope before and after the wet etching in potassium hydroxide(KOH)solution.The morphology was studied by the optical microscope and atomic force microscope.The crystalline quality was characterized by the x-ray diffraction.The lateral coherence length,the tilt angle,the vertical coherence length,and the vertical lattice-strain were acquired using the pseudo-Voigt function to fit the x-ray diffraction curves and then calculating with four empirical formulae.The lateral coherence length increases with the misorientation angle,because higher step density and shorter distance between adjacent steps can lead to larger lateral coherence length.The tilt angle increases with the misorientation angle,which means that the misoriented substrate can degrade the identity of crystal orientation of the N-polar GaN film.The vertical lattice-strain decreases with the misorientation angle.The vertical coherence length does not change a lot as the misorientation angle increases and this value of all samples is close to the nominal thickness of the N-polar GaN layer.This study helps to understand the influence of the misorientation angle of misoriented C-plane sapphire on the morphology,the crystalline quality,and the microstructure of N-polar GaN films.

Xiaotao Hu;Yimeng Song;Zhaole Su;Haiqiang Jia;Wenxin Wang;Yang Jiang;Yangfeng Li;Hong Chen

Key Laboratory for Renewable Energy,Beijing Key Laboratory for New Energy Materials and Devices,Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;School of Mathematics and Physics,Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science,University of Science and Technology Beijing,Beijing 100083,China;Songshan Lake Materials Laboratory,Dongguan 523808,China;College of Materials Science and Opto-Electronic Technology,University of Chinese Academy of Sciences,Beijing 100049,China

中国物理B（英文版）

[1]Xiaotao Hu;Yimeng Song;Zhaole Su;Haiqiang Jia;Wenxin Wang;Yang Jiang;Yangfeng Li;Hong Chen-.Characterization of the N-polar GaN film grown on C-plane sapphire and misoriented C-plane sapphire substrates by MOCVD)[J].中国物理B（英文版）,2022(03):149-154

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