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2021 ◽  
Author(s):  
Xiaotao Hu ◽  
Yimeng Song ◽  
Zhaole Su ◽  
Haiqiang Jia ◽  
Wenxin Wang ◽  
...  

Abstract 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 near 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.


2021 ◽  
Vol 5 ◽  
pp. 100106
Author(s):  
Shubhendra Kumar Jain ◽  
Pratibha Goel ◽  
Urvashi Varshney ◽  
Tushar Garg ◽  
Neha Aggarwal ◽  
...  

2021 ◽  
Vol 28 (1) ◽  
pp. 014006
Author(s):  
Anja Vanleenhove ◽  
Charlotte Zborowski ◽  
Inge Vaesen ◽  
Ilse Hoflijk ◽  
Thierry Conard
Keyword(s):  

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 234
Author(s):  
Jae-Hoon Lee ◽  
Ki-Sik Im

A crack-free GaN film grown on 4-inch Si (111) substrate is proposed using two-step growth methods simply controlled by both III/V ratio and pressure. Two-step growth process is found to be effective in compensating the strong tensile stress in the GaN layer grown on Si substrate. The high-resolution X-ray diffraction (XRD) rocking curves of (002) and (102) planes for the GaN epitaxial layer with two-step growth method are 317 and 432 arcsec, while the corresponding values for the reference sample without two-step growth method are 550 and 1207 arcsec, respectively. The reduced threading dislocation of GaN film with two-step growth method is obtained to be ~2 × 108/cm2, which is attributed to effectively annihilate and bend threading dislocation.


Author(s):  
Shiying Zhang ◽  
Lei Zhang ◽  
Yueyao Zhong ◽  
Guodong Wang ◽  
Qingjun Xu

High crystal quality GaN nanorod arrays were fabricated by inductively coupled plasma (ICP) etching using self-organized nickel (Ni) nano-islands mask on GaN film and subsequent repaired process including annealing in ammonia and KOH etching. The Ni nano-islands have been formed by rapid thermal annealing, whose density, shape, and dimensions were regulated by annealing temperature and Ni layer thickness. The structural and optical properties of the nanorods obtained from GaN epitaxial layers were comparatively studied by high-resolution X-ray diffraction (HRXRD), Raman spectroscopy and photoluminescence (PL). The results indicate that damage induced by plasma can be successfully healed by annealing in NH3 at 900 °C. The average diameter of the as-etched nanorod was effectively reduced and the plasma etch damage was removed after a wet treatment process in a KOH solution. It was found that the diameter of the GaN nanorod was continuously reduced and the PL intensity first increased, then reduced and finally increased as the KOH etching time sequentially increased.


2020 ◽  
Vol 20 (12) ◽  
pp. 7553-7557
Author(s):  
Bang Liu ◽  
Naisen Yu ◽  
Dedi Liu ◽  
Benkang Liu ◽  
Yunfeng Wu ◽  
...  

High performance p-GaN/oxide layer/n-GaN ultraviolet (UV) photodetector was fabricated in this paper. The UV detector composed of n-GaN and p-GaN film with oxide layer which was constructed by directly contacting way. The detector based on GaN p-GaN/oxide layer/n-GaN structure showed high UV response with fast speed. The results indicated that the fabrication of large-scale GaNbased materials was greatly facilitated with relatively low cost contacting method. Furthermore, it offered a new method to obtain UV detector for GaN-based materials with high performance.


Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5118
Author(s):  
Jinxing Wu ◽  
Peixian Li ◽  
Shengrui Xu ◽  
Xiaowei Zhou ◽  
Hongchang Tao ◽  
...  

Magnetron sputtering is adopted to deposit ~25 nm thick AlN on the surface of hexagonal BN(h-BN)/sapphire substrates, followed by epitaxial GaN growth on top of the AlN/h-BN/sapphire substrate using a metal–organic chemical vapor deposition system. Compared to GaN grown on the h-BN/sapphire surface directly, this method results in a continuous and smooth GaN film with a smaller root mean square roughness. Besides, the introduction of the sputtered AlN layer reduces the dislocation density of GaN by 35.7%. We provide a pathway of GaN epitaxy on the h-BN surface, which significantly improves its surface morphology and crystal quality.


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