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Crystallographic wing tilt and thermal-stress distribution of GaN laterally overgrown on maskless V-grooved sapphire substrate by metal-organic chemical vapor deposition

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7 Author(s)
Xing, Zhigang ; Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China ; Wang, J. ; Wang, Y. ; Wang, X.H.
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The crystallographic wing tilt, commonly observed for laterally overgrown GaN films, has been essentially overcome by the authors’ newly developed GaN lateral-epitaxial overgrowth (LEO) method or the so-called cantibridge epitaxy (CBE), which employs a maskless V-grooved c-plane sapphire as the substrate. The absence of the void between the coalesced wings in the CBE GaN films is found to be a key factor for the elimination of the wing tilt in the absence of any mask material. Finite element analysis is performed for voided and nonvoided CBE GaN samples. This analysis verified the correlation between the coalescence void and the crystallographic wing tilt. Thermal-stress distribution in the GaN film is presented as well. The agreement between the measured and simulated tilt angles denotes that the essence of the crystallographic wing tilt in the maskless LEO GaN films is not the same as that of the conventional LEO GaN film with a mask, which did not develop during the epitaxy process, but instead in the cooldown after growth. The crystallographic tilt angle and the stress fluctuation have been drastically suppressed, even in the voided CBE GaN film. Additional micro-Raman mapping measurements also give results in agreement with the simulated thermal-stress distribution.

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures  (Volume:25 ,  Issue: 3 )