Browsing by Author "Yang, Din-Ru"

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Method for modulating the wafer bow of free-standing GaN substrates via inductively coupled plasma etching
(2010-12-01)
Chen, Kuei-Ming
;
Yeh, Yen-Hsien
;
Wu, Yin-Hao
;
Chiang, Chen-Hao
;
Yang, Din-Ru
The bowing curvature of the free-standing GaN substrate significantly decreased almost linearly from 067 to 0 056 m(-1) (i e the bowing radius increased from 1 5 to 178 m) with increase in inductively coupled plasma (ICP) etching time at the N-polar face and eventually changed the bowing direction from convex to concave Furthermore the Influences of the bowing curvature on the measured full width at half maximum (FWEIM) of high-resolution X-ray diffraction (HRXRD) in (0 0 2) reflection were also deduced which reduced from 176 8 to 888 arcsec with increase in ICP etching time Decrease in the nonhomogeneous distribution of threading dislocations and point defects as well as V(Ga)-O(N) complex defects on removing the GaN layer from N-polar face which removed large amount of defects was one of the reasons that improved the bowing of the free-standing GaN substrate Another reason was the high aspect ratio of needle-like GaN that appeared at the N-polar face after ICP etching which released the compressive strain of the free-standing GaN substrate By doing so crack-free and extremely flat free-standing GaN substrates with a bowing radius of 178 m could be obtained (C) 2010 Elsevier B V All rights reserved
Stress and Defect Distribution of Thick GaN Film Homoepitaxially Regrown on Free-Standing GaN by Hydride Vapor Phase Epitaxy
(2010)
Chen, Kuei-Ming
;
Yeh, Yen-Hsien
;
Wu, Yin-Hao
;
Chiang, Chen-Hao
;
Yang, Din-Ru
A 220-mu m-thick Gallium nitride (GaN) layer was homoepitaxially regrown on the Ga-polar face of a 200-mu m-thick free-standing c-plane GaN by hydride vapor-phase epitaxy (HVPE). The boundary of the biaxial stress distribution in the GaN substrate after regrowth was clearly distinguished. One half part, the regrown GaN, was found to be more compressive than the other half part, the free-standing GaN. Additionally, the densities of the screw and mixed dislocations reduced from 2.4 x 10(7) to 6 x 10(6) cm(-2) after regrowth. Furthermore, the yellow band emission almost disappeared, accompanied by a peak emission at approximately 380 nm related to the edge dislocation was under slightly improved in regrown GaN. We conclude that the reduction of the dislocation defects and Ga vacancies and/or O impurities are the two main reasons for the higher compressive stress in the regrown GaN than in the free-standing GaN, causing the curvature of the GaN substrate to be twice concave after regrowth. (C) 2010 The Japan Society of Applied Physics