Browsing by Author "Chen, Hou-Guang"

Now showing 1 - 11 of 11

Dislocation reduction in GaN grown on stripe patterned r-plane sapphire substrates
(2007-07-09)
Chen, Hou-Guang
;
Ko, Tsung-Shine
;
Ling, Shih-Chun
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
Extended defect reduction in GaN can be achieved via direct growth on stripe patterned (1(-)1 02) r-plane sapphire substrates by metal organic chemical vapor deposition. The striped mesa is along [11 (-)2 0] with two etched sides in {0001} and {1 (-)1 01} faces. GaN grown on both etched facets in epitaxy exhibit different crystallographic relationships with sapphire substrate which are (1 (-)1 02)(sapphire)parallel to(11 (-)2 0)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), and (0001)(sapphire)parallel to(0001)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), respectively. The dislocation densities can be significantly reduced through epitaxial growth on the inclined lateral faces of mesas. Dislocation density in the order of similar to 10(7) cm(-2) can be achieved in the tilted GaN. (C) 2007 American Institute of Physics.
Fabrication of microcavity light-emitting diodes using highly reflective AlN-GaN and Ta2O5-SiO2 distributed Bragg mirrors
(2007-07-01)
Huang, G. S.
;
Lu, T. C.
;
Kuo, H. C.
;
Wang, S. C.
;
Chen, Hou-Guang
We report the fabrication of microcavity light-emitting diodes (MCLEDs) with high reflectivity and crack-free AIN-GaN distributed Bragg reflector (DBR). The 5 lambda microcavity structure consists of an n-type GaN, ten pairs InGaN-GaN multiple quantum wells and p-type GaN sandwiched between the hybrid cavity mode of an AIN-GaN and a Ta2O5-SiO2 DBR. The AIN-GaN DBR has 29 periods with insertion of six AIN-GaN superlattice layers showing a crack-free surface morphology and a high peak reflectivity of 99.4% with a stopband of 21 nm. The output power of MCLED is about 11 mu W at an injection current of 7 mA. The electroluminescence has a polarization property with a degree of polarization of about 51 %.
Growth of diamond nanoplatelets by CVD
(2008-07-01)
Chen, Hou-Guang
;
Chang, Li
;
Cho, Shih-Yin
;
Yan, Jhih-Kun
;
Lu, Chun-An
Hexagonal, single-crystalline, diamond nanoplatelets synthesized by microwave plasma (MP)CVD on Au-Ge alloy and nanocrystalline diamond (nc-diamond) film substrates, respectively, are reported. On the nc-diamond matrix, hexagonal diamond nanoplatelets can grow to a thickness of as little as approximately 10 nm. The effects of various processing parameters, such as methane concentration, microwave power, and gas pressure, on the growth of diamond nanoplatelets are explored. High-resolution transmission electron microscopy (HRTEM) reveals that the diamond nanoplatelets contain multi-parallel twins, and the side faces of the platelets exhibit {100}/{111} ridge-and-trough structure. Anisotropic growth of diamond nanoplatelet is believed to result from the side face structure of the twinned platelets and intensive plasma reaction.
Growth of diamond nanoplatelets on nanocrystalline diamond substrates
(2009-02-01)
Chen, Hou-Guang
;
Chang, Li
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We report the growth of single crystalline diamond nanoplatelets (DNPs) on different types of nanocrystalline diamond substrates by high temperature microwave-plasma chemical vapor deposition. The influence of methane concentration on DNP morphologies has been studied. According to high-resolution transmission electron microscopy observation, DNPs are typical tabular twined crystallites which consist of several twin lamellae parallel to platelet surfaces and the side-face structure of DNPs is the ridge-and-trough structure consisting of {100} and {111} faces. The field emission properties of DNPs with various morphologies and nano-crystalline diamond substrates were characterized. The turn-on electrical field of DNPs with well-faceted side edges was lower in comparison with the DNPs with irregular shapes and nanocrystalline-diamond substrate. (C) 2008 Elsevier B.V. All rights reserved.
Growth of epitaxial ZnO thin film on yttria-stabilized zirconia single-crystal substrate
(2007-01-01)
Chao, Yen-Cheng
;
Lin, Chih-Wei
;
Ke, Dong-Jie
;
Wu, Yue-Han
;
Chen, Hou-Guang
ZnO growth on yttria-stabilized zirconia (YSZ) (I 1 1) single-crystal substrate has been carried out by metalorganic chemical vapor deposition (MOCVD). High-quality epitaxial ZnO has been evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Cross-sectional TEM from all deposited films reveals that the interface between ZnO and YSZ is atomically flat, and orientation relationship is deduced to be [1 (1) over bar 100](ZnO//)[11 (2) over bar](YSZ,) (2 (1) over bar(1) over bar0)(ZnO)//[001](YSZ) and (0 0 0 2)(ZnO)//(111)(YSZ). It has been found that surface roughness increases with the substrate temperature in the range of 500-700 degrees C. The growth rate also varies with the temperature. (c) 2006 Elsevier B.V. All rights reserved.
Hybrid nitride microcavity using crack-free highly reflective AlN/GaN and Ta2O5/SiO2 distributed Bragg mirrors
(2007-06-01)
Huang, G. S.
;
Chen, Hou-Guang
;
Chen, J.-R.
;
Lu, T. C.
;
Kuo, H. C.
We report the growth over 2 inch sapphire substrates of hybrid nitride-based microcavities using one crack-free highly reflective AIN/GaN distributed Bragg reflectors (DBRs) incorporated with AIN/GaN superlattice (SL) insertion layers and Ta2O5/SiO2 DBRs. The optical cavity is formed by a 5 lambda cavity consisting of n-type GaN, 10 pairs multiple quantum wells and p-type GaN sandwiched by AIN/GaN and Ta2O5/SiO2 DBRs. Reflectivity and photoluminescence measurements were carried out on these structures. A 29 periods AIN/GaN DBR incorporated with six AN/GaN superlattice insertion layers showed no observable cracks and achieved a peak reflectivity of 99.4% and a stopband of 21 run. Based on these high quality DBRs, the cavity mode is clearly resolved with a linewidth of 2.6 nm. These results demonstrate that the AIN/GaN system is very promising for the achievement of strong light-matter interaction and the fabrication of nitride-based vertical cavity surface emitting lasers. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Investigation on microstructure in GaN epitaxial growth on the stripe-patterned r-plane sapphire substrates
(2008-04-01)
Chen, Hou-Guang
;
Ko, Tsung-Shine
;
Chang, Li
;
Wu, Yue-Han
;
Lu, Tien-Chang
This study reports on the reduction of dislocations in the GaN grown on the stripe-patterned r-plane sapphire substrates via metal-organic chemical vapor deposition (MOCVD). The stripes oriented along the sapphire [1 1 (2) over bar 0] direction with asymmetrical side faces were fabricated by lithographic and wet-etching processes. The two etching sides of sapphire-striped mesa are {0 0 0 1} and {1 (1) over bar 0 1} faces. GaN grown on both etching facets exhibits different epitaxial relationships with the sapphire substrate. The GaN grown from the {0 0 0 1} side face of the sapphire mesa contains a low-dislocation density in the order of 10(7) cm(-2). The interfacial regions between the GaN and patterned sapphire substrate are also studied to clarify the behavior of GaN epitaxial growth on the inclined sapphire faces and defect-reduction mechanism. (C) 2007 Elsevier B.V. All rights reserved.
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.
Strong ultraviolet emission from InGaN/AlGaN multiple quantum well grown by multi-step process
(2007-04-01)
Chen, Hou-Guang
;
Hsu, Nai-Fang
;
Chu, Jung-Tang
;
Yao, Hsin-Hung
;
Lu, Tien-Chang
We propose a method of realizing strong ultraviolet emission from InGaN/AlGaN multiple quantum wells (MQWs) grown by a multi-step process. During growth of the quantum well layer, only trimethylindium (TMIn) and ammonia were introduced into the reactor, followed by a growth interruption treatment before growth of AlGaN barriers. The growth temperature of QWs dominates the photoluminescence (PL) emission peak position and surface morphologies of the films. It was found that the PL spectra of the samples with MQWs grown at 685 degrees C showed a strong UV emission at 380 nm. The correlation between surface structures and optical characteristics was studied by cathodoluminescence microscopy. The electroluminescence spectra under various injection currents showed a weak carrier localization effect induced by a quantum-confined Stark effect in the MQW.
Structural and nanomechanical properties of a-plane ZnO thin films deposited under different oxygen partial pressures
(2012-05-01)
Jian, Sheng-Rui
;
Chen, Hou-Guang
;
Chen, Guo-Ju
;
Jang, Jason S. C.
;
Juang, Jenh-Yih
The effects of O-2 partial pressure during RF magnetron sputtering on the structural and nanomechanical properties of a-plane ZnO thin films were investigated by using X-ray diffraction (XRD) and nanoindentation techniques. The XRD and the transmission electron microscopy (TEM) selected area diffraction results indicate that the epitaxial relationship between ZnO thin films and Al2O3 substrates is ZnO (11 (2) over bar0)//Al2O3 (1 (1) over bar 02). The average values of the hardness and Young's modulus of the a-plane ZnO films were found to decrease with increasing oxygen partial pressure. The cross-sectional TEM revealing the localized plastic deformation of ZnO thin films beneath the Berkovich indenter, indicating the prominent role played by the threading dislocations in the film deformation behavior. At higher indentation loadings, the sapphire substrate exhibits extensive deformation with narrow slip bands appearing on {0001} plane. However, no evidence of pressure-induced phase transformation, as well as cracking and/or delamination phenomena at the film-substrate interface was observed. (C) 2011 Elsevier B.V. All rights reserved.
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.