Browsing by Author "Lin, Yun-Hsiang"

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High-quality and highly-transparent AlN template on annealed sputter-deposited AlN buffer layer for deep ultra-violet light-emitting diodes
(2017-05-01)
Huang, Chia-Yen
;
Wu, Pei-Yu
;
Chang, Kai-Shiang
;
Lin, Yun-Hsiang
;
Peng, Wei-Chih
A high-quality and highly-transparent AlN template was prepared by regrowth on a sputter-deposited AlN buffer layer. The buffer layer was thermally annealed and then underwent AlN regrowth in metalorganic chemical vapor deposition (MOCVD). The peakwidth of (002) and (102) plane x-ray rocking curve was 104 arcsec and 290 arcsec, respectively, indicating a threading dislocation density <5.0 x 10(8) cm(-2). Dislocations were reduced via grain growth and morphological evolution. The absence of carbon impurity source in sputter deposition also resulted in an improved transparency. According to transmission and reflection measurements, the absorption rate of lambda=280 nm emission propagating through the template was less than 6%. (C) 2017 Author(s).
The origin and mitigation of volcano-like morphologies in micron-thick AlGaN/AlN heteroepitaxy
(2017-08-14)
Huang, Chia-Yen
;
Chang, Kai-Shiang
;
Huang, Cheng-Yao
;
Lin, Yun-Hsiang
;
Peng, Wei-Chih
We investigated the origin of morphological instability in 2 mu m thick Al0.6Ga0.4N/AlN heteroepitaxy. The primary morphology was driven by the residual epitaxial strain, forming hill-like morphologies via surface diffusion. The secondary morphology was driven by the interaction between the primary morphology and dislocation clusters in the epitaxial layers. The difference in the local growth rate yields volcano-like morphologies centering on deep pits. Insertion of multi-stack superlattice transition layers between AlGaN and GaN effectively suppressed the secondary morphologies by simultaneously pre-relaxing the template and filtering treading dislocations. Published by AIP Publishing.