Browsing by Author "Wang, Sing-Chung"

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Internal quantum efficiency behavior of a-plane and c-plane InGaN/GaN multiple quantum well with different indium compositions
(2008)
Wang, Te-Chung
;
Ko, Tsung-Shine
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
;
Gao, Run-Ci
We had investigated the potential of non-polar a-plane InGaN/GaN multiple quantum well (MQW) for high indium content blue/green emission. By comparisons of a-plane and c-plane MQW with different indium, compositions, we concluded that without piezoelectric field, high indium. content non-polar a-plane InGaN/GaN MQW is suitable for green light emitting diode (LED). Furthermore, similar to c-plane GaN InGaN/GaN MQW, the localized state might enhance the performance of a-plane MQW while the indium composition about 24% although the threading dislocation density (TDD) is quite high. On the other hand, the indium phase separation might also occur on a-plane InGaN/GaN MQW while the indium. composition about 30% so that the photoluminescence intensity of the sample 810 degrees C low down and spectrum bandwidth broaden.
Material and optical properties of trenched epitaxial lateral overgrowth of a-plane GaN
(2007)
Wang, Te-Chung
;
Lu, Tien-Chang
;
Ko, Tsung-Shine
;
Kuo, Hao-Chung
;
Chen, Hou-Guang
The crystal quality of a-plane GaN film was successfully improved by using trenched epitaxial lateral overgrowth (TELOG) of a-plane GaN. Not only the threading dislocation density but also the difference of anisotropic in-plane strain between orthogonal crystal axes can be mitigated by using TELOG. The low threading dislocation density investigated by transmission electron microscopy was estimated to be 3 x 10(7) cm(-2) on the N-face GaN wing. According the results of mu-PL and CL, the threading dislocations are the strongly non-radiative center in a-plane GaN film. Finally, we concluded that a narrower stripped GaN seeds and deeper stripped trenches etched into the surface of sapphire could derive a better quality a-plane GaN film.
Trenched epitaxial lateral overgrowth of fast coalesced a-plane GaN with low dislocation density
(2006-12-18)
Wang, Te-Chung
;
Lu, Tien-Chang
;
Ko, Tsung-Shine
;
Kuo, Hao-Chung
;
Yu, Min
The crystal quality of a-plane GaN films was improved by using epitaxial lateral overgrowth on trenched a-plane GaN buffer layers. Not only the threading dislocation density but also the difference of anisotropic in-plane strain between orthogonal crystal axes can be mitigated by using trenched epitaxial lateral overgrowth (TELOG). The low threading dislocation density investigated by the cross-sectional transmission electron microscopy was estimated to be 3x10(7) cm(-2) on the N-face GaN wing. On the other hand, the Ga-face GaN wing with a faster lateral overgrowth rate could be influenced by the thin GaN layer grown on the bottom of the trenches, resulting in higher dislocation density generated. As a result, the authors concluded that a narrower stripped GaN seeds and deeper stripped trenches etched into the surface of sapphire could derive a better quality a-plane GaN film. Finally, they demonstrated the fast coalescence process of TELOG GaN films below 10 mu m thick. (c) 2006 American Institute of Physics.