Browsing by Author "Chang, Shoou-Jinn"

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Effect of V/III Ratios on Surface Morphology in a GaSb Thin Film Grown on GaAs Substrate by MOCVD
(2014-01-01)
Hsiao, Chih-Jen
;
Liu, Chun-Kuan
;
Huynh, Sa-Hoang
;
Minh, Thien-Huu Ha
;
Yu, Hung-Wei
The epitaxial growth of GaSb thin film with different V/III ratios on high-lattice-mismatched GaAs (001) substrates by metal organic chemical vapor deposition (MOCVD) was investigated. Under optimal V/III ratio of 2.5, we found that there are many periodic 90 degrees interfacial misfit dislocation (IMF) arrays existing at the GaAs/GaSb interface. The surface roughness is about 3.6nm, 2.2nm, 3.8nm, respectively while different V/III ratios (1.25, 2.5, 5) were adopted. These results demonstrated that the hill-and valley structure on the surface of GaSb/GaAs heterostructure can be effectively improved, and formed smooth surface morphology.
Efficiency Enhancement in InGaN Photovoltaic Cells With Inverted Textured Surface
(2017-08-15)
Wu, Ming-Hsien
;
Horng, Ray-Hua
;
Liao, Wen-Yih
;
Chang, Sheng-Po
;
Chang, Shoou-Jinn
We report on the improvement of conversion efficiency of InGaN photovoltaic (PV) cells with inverted textured surface (ITS). InGaN PV cells with ITS showed short-circuit current density and conversion efficiency of 0.63 mA/cm(2) and 1.01%, which are 68.17% and 73.33% higher than the characteristics of conventional InGaN PV cells, respectively. The improvement can be attributed to the reduction of both the shading effect of the electrode contact pad and surface reflection of the incident irradiation under one-sun air-mass 1.5-G illumination (100 mW/cm(2)).
Enhanced Extraction and Efficiency of Blue Light-Emitting Diodes Prepared Using Two-Step-Etched Patterned Sapphire Substrates
(2009)
Lin, Ray-Ming
;
Lu, Yuan-Chieh
;
Yu, Sheng-Fu
;
Wu, YewChung Sermon
;
Chiang, Chung-Hao
Using a hot acid wet etching method, we have fabricated two types of patterned sapphire substrates: A pyramidal patterned sapphire substrate (PPSS) and a flat-top patterned sapphire substrate (FTPSS). After placing these samples into an atmospheric pressure metallorganic chemical vapor deposition system, we deposited standard InGaN light-emitting diode (LED) structures onto their surfaces. The crystal quality of these two surfaces was enhanced, as evidenced using X-ray diffraction (the full width at half-maximum decreased from 406.8 arcsec for the conventional sapphire to 356.4 and 349.2 arcsec for the PPSS and FTPSS samples, respectively). The output power of InGaN-based blue LEDs incorporating the PPSS and FTPSS improved to 17.9 and 18.7%, respectively, at 20 mA. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3231502] All rights reserved.
GaN-based light-emitting diodes with graphene/indium tin oxide transparent layer
(2014-03-10)
Lai, Wei-Chih
;
Lin, Chih-Nan
;
Lai, Yi-Chun
;
Yu, Peichen
;
Chi, Gou Chung
We have demonstrated a gallium nitride (GaN)-based green light-emitting diode (LED) with graphene/indium tin oxide (ITO) transparent contact. The ohmic characteristic of the p-GaN and graphene/ITO contact could be preformed by annealing at 500 degrees C for 5 min. The specific contact resistance of p-GaN/graphene/ITO (3.72E-3 Omega(center dot)cm(2)) is one order less than that of p-GaN/ITO. In addition, the 20-mA forward voltage of LEDs with graphene/ITO transparent (3.05 V) is 0.09 V lower than that of ITO LEDs (3.14 V). Besides, We have got an output power enhancement of 11% on LEDs with graphene/ITO transparent contact. (C)2014 Optical Society of America
Growth of ultrathin GaSb layer on GaAs using metal-organic chemical vapor deposition with Sb interfacial treatment
(2016-09)
Hsiao, Chih-Jen
;
Minh-Thien-Huu Ha
;
Hsu, Ching-Yi
;
Lin, Yueh-Chin
;
Chang, Sheng-Po
GaSb epitaxial layers were directly grown on GaAs substrates by metal-organic chemical vapor deposition involving Sb interfacial treatment with optimized growth temperature and V/III ratio. The interfacial treatment effectively reduces the surface energy and strain energy difference, resulting in a quasi-2D growth mode. When the GaSb layer was grown at 520 degrees C, the strain induced by lattice mismatch was accommodated by 90 degrees dislocations with a period of 5.67 nm. By optimizing the V/III ratio, the surface roughness of the ultrathin GaSb/GaAs heterostructure was reduced, resulting in a reduced carrier scattering and improved electronic properties. (C) 2016 The Japan Society of Applied Physics
Light Emitting Diodes
(2015-01-01)
Lin, Chien-Chung
;
Chen, Kuo-Ju
;
Lin, Da-Wei
;
Han, Hau-Vie
;
Lai, Wei-Chih
Low threshold current, low resistance 1.3 mu m InAs-InGaAs quantum-dot VCSELs with fully doped DBRs grown by MBE
(2007-01-01)
Yu, Hsin-Chieh
;
Wang, Jyh-Shyang
;
Su, Yan-Kuin
;
Chang, Shoou-Jinn
;
Kuo, Hao-Chung
The processing technology of 1.3 mu m InAs-InGaAs quantum-dot VCSELs with fully doped DBRs grown by MBE will be demonstrated. The threshold currents of the fabricated devices with 10 mu m oxide-confined aperture are 0.7mA, which correspond to 890A/cm(2) threshold current density. And the threshold voltage of the device is 1.03V and maximum output power is 33 M. The series resistance is 85 Omega which is 10 times lower then our preliminary work and 3 times lower then intracavity contacted InAs-InGaAs quantum-dot VCSEL. This relatively lower resistance can even comparable with the best result reported in InGaAs oxide-confined VCSELs with intracavity contact.
Performance improvement of highly mismatched GaSb layers on GaAs by interfacial-treatment-assisted chemical vapor deposition
(2017-01)
Hsiao, Chih-Jen
;
Minh-Thien-Huu Ha
;
Liu, Chun-Kuan
;
Hong-Quan Nguyen
;
Yu, Hung-Wei
Strain-relieved GaSb quantum dots on GaAs can be achieved by either periodic interfacial misfit (IMF) or the conventional Stranski-Krastanov (SK) growth modes by changing the growth parameters. In this study, the Sb interfacial treatment was employed to improve the GaSb crystal quality including low defect density, smooth surface morphology, and high hole mobility. This technique yields two-dimensional (2D) islands with a height as low as 1.7 nm and width up to 190 nm in the IMF growth mode. In contrast to the interfacial treatments conventionally employed in the initial strain relaxation of GaSb/GaAs hererostructure, the Sb treatment promotes the formation of strong Ga-Sb bonds on the surface of the grown island, which effectively reduces the interfacial free energy and thus promotes the formation of 2D islands. With the Sb interfacial treatment, a high-relaxation 100-nm GaSb epilayer was grown on the GaAs substrate, the epilayers was strain relaxed and exhibited enhanced electrical properties with a high hole mobility of similar to 667 cm(2) V-1 s(-1) and with superior optical properties as evidenced by the photoluminescence B-line peak. The results of this study demonstrate an effective interfacial-treatment growth technique to relax the initial strain for the highly mismatched GaSb layers grown on a GaAs substrate.
Symmetrical Dipole Contribution from Planar Defects on m-plane ZnO Epitaxial Films
(2014-01-01)
Liu, Chung-Wei
;
Chang, Shoou-Jinn
;
Ho, Yen-Teng
;
Chang, Li
;
Lo, Kuang-Yao
The planar defects such as basal stacking faults (BSFs) are probed on m-plane ZnO grown on LaAlO3(112) substrate by reflective second harmonic generation (RSHG). The BSFs result in nonvanishing single-direction dipoles that behave similar to a mirror-like symmetrical dipole. The RSHG pattern from m-plane ZnO comprised of not only the bulk dipole contribution of ZnO but also an additional mirror-like symmetrical dipole contribution from BSF defects. Transmission electron microscopy image displays the presence of BSFs that lie in the c-plane of ZnO and agrees well with RSHG results. Planar BSFs are formed due to the anisotropic stress relaxation between m-plane ZnO film and LaAlO3(112) substrate, resulting in higher-quality m-plane ZnO films.