Browsing by Author "Su, Yan-Kuin"

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Cathodoluminescence studies of GaAs nano-wires grown on shallow-trench-patterned Si
(2010-11-19)
Lee, Ling
;
Fan, Wen-Chung
;
Ku, Jui-Tai
;
Chang, Wen-Hao
;
Chen, Wei-Kuo
The optical properties of GaAs nano-wires grown on shallow-trench-patterned Si(001) substrates were investigated by cathodoluminescence. The results showed that when the trench width ranges from 80 to 100 nm, the emission efficiency of GaAs can be enhanced and is stronger than that of a homogeneously grown epilayer. The suppression of non-radiative centers is attributed to the trapping of both threading dislocations and planar defects at the trench sidewalls. This approach demonstrates the feasibility of growing nano-scaled GaAs-based optoelectronic devices on Si substrates.
Cathodoluminescence studies of GaAs nano-wires grown on shallow-trench-patterned Si
(2010-11-19)
Lee, Ling
;
Fan, Wen-Chung
;
Ku, Jui-Tai
;
Chang, Wen-Hao
;
Chen, Wei-Kuo
The optical properties of GaAs nano-wires grown on shallow-trench-patterned Si(001) substrates were investigated by cathodoluminescence. The results showed that when the trench width ranges from 80 to 100 nm, the emission efficiency of GaAs can be enhanced and is stronger than that of a homogeneously grown epilayer. The suppression of non-radiative centers is attributed to the trapping of both threading dislocations and planar defects at the trench sidewalls. This approach demonstrates the feasibility of growing nano-scaled GaAs-based optoelectronic devices on Si substrates.
Effect of AlInGaN barrier layers with various TMGa flows on optoelectronic characteristics of near UV light-emitting diodes grown by atmospheric pressure metalorganic vapor phase epitaxy
(2011-08-01)
Fu, Yi-Keng
;
Lu, Yu-Hsuan
;
Jiang, Ren-Hao
;
Chen, Bo-Chun
;
Fang, Yen-Hsiang
Near ultraviolet light-emitting diodes (LEDs) with quaternary AlInGaN quantum barriers (QBs) are grown by atmospheric pressure metalorganic vapor phase epitaxy. The indium mole fraction of AlInGaN QB could be enhanced as we increased the TMG flow rate. Both the wavelength shift in EL spectra and forward voltage at 20 mA current injection were reduced by using AlInGaN QB. Under 100 mA current injection, the LED output power with Al(0.089)In(0.035)Ga(0.876)N QB can be enhanced by 15.9%, compared to LED with GaN QB. It should be attributed to a reduction of lattice mismatch induced polarization mismatch in the active layer. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
Electron Emission Enhanced Properties of Gold Nanoparticle-Decorated ZnO Nanosheets Grown at Room Temperature
(2018-12-01)
Wang, Zi-Hao
;
Yang, Chih-Chiang
;
Yu, Hsin-Chieh
;
Peng, Yu-Ming
;
Su, Yan-Kuin
In this study, gold nanoparticles were adsorbed on glass nanosheets (NSs) grown on the surface of glass substrates with aqueous solutions at room temperature. The diameter and length of gold coater ZnO NSs are approximately 50 nm and 0.9 mu m, respectively. The Au-decorated ZnO NS grown at room temperature is structurally uniform and has a good orientation of the wurtzite structure. The turn-on electric fields of ZnO and Au-decorated ZnO nanosheets were 6.04 and 4.91 V/mu m, respectively. The field-enhancement factors were 2507 and 9298, respectively. Results showed that the Au-decorated ZnO NS has enhanced field-emission properties. In addition, due to the reduced size of the protruding Au nanoparticles, the number of emitting sites increases.
Electron Field Emission Enhancement Based on Al-Doped ZnO Nanorod Arrays With UV Exposure
(2018-01-01)
Wang, Zi-Hao
;
Yang, Chih-Chiang
;
Yu, Hsin-Chieh
;
Yeh, Hsin-Ting
;
Peng, Yu-Ming
In this paper, Al-doped ZnO nanorods (AZO NRs) were successfully applied on glass substrates through hydrothermal synthesis growth with a fabrication field-emission (FE) device. The enhanced FE properties of AZO NRs were measured. The turn-on fields were reduced by 2.35 and 1.51 V/mu m in the dark and under UV light, and the enhanced field enhancement factors (beta) were 5708 and 10137, respectively. Results show that the FE performances of AZO NRs were enhanced by the combined effect of increased carrier concentration and UV light illumination.
Hole Injection and Electron Overflow Improvement in 365 nm Light-Emitting Diodes by Band-Engineering Electron Blocking Layer
(2013-08-01)
Fu, Yi-Keng
;
Lu, Yu-Hsuan
;
Xuan, Rong
;
Chen, Jenn-Fang
;
Su, Yan-Kuin
The work reports a theoretical and experimental study on the device performance of near ultraviolet light-emitting diodes (LEDs) with specific design on the electron blocking layer (EBL) by employing the band-engineering. The simulation results show the polarization-induced downward band bending is mitigated in the specific EBL design and, hence, the capability of hole transportation increases and the behavior of electron overflow decreases. The experimental results show the LEDs with specific EBL design exhibited a reduction of forward voltage from 4.40 to 4.07 V and a much enhancement of light output power from 30.6 to 51.9mW, compared with conventional LED. (C) 2013 The Japan Society of Applied Physics
Impact of Oxygen Vacancy on the Photo-Electrical Properties of In2O3-Based Thin-Film Transistor by Doping Ga
(2019-03-01)
Chen, Kuan-Yu
;
Yang, Chih-Chiang
;
Su, Yan-Kuin
;
Wang, Zi-Hao
;
Yu, Hsin-Chieh
In this study, amorphous indium gallium oxide thin-film transistors (IGO TFTs) were fabricated by co-sputtering. Three samples with different deposition powers of the In2O3 target, namely, sample A with 50 W deposition power, sample B with 60 W deposition power, and sample C with 70 W deposition power, were investigated. The device performance revealed that oxygen vacancies are strongly dependent on indium content. However, when the deposition power of the In2O3 target increased, the number of oxygen vacancies, which act as charge carriers to improve the device performance, increased. The best performance was recorded at a threshold voltage of 1.1 V, on-off current ratio of 4.5 x 10(6), and subthreshold swing of 3.82 V/dec in sample B. Meanwhile, the optical properties of sample B included a responsivity of 0.16 A/W and excellent ultraviolet-to-visible rejection ratio of 8 x 10(4). IGO TFTs may act as photodetectors according to the results obtained for optical properties.
Improved Performance of InGaN/GaN Light-Emitting Diodes With Thin Intermediate Barriers
(2011-11-15)
Chen, Bo-Chun
;
Chang, Chun-Yen
;
Fu, Yi-Keng
;
Huang, Kai-Feng
;
Lu, Yu-Hsuan
In this work, the performance of blue InGaN/GaN light-emitting diodes (LEDs) with thin intermediate barriers at high injection current is investigated. From the experimental results, it is found that the performance of LEDs with intermediate 5-nm-thick barriers is improved about 15% at 200 mA, compared with the sample with unique 9-nm-thick barriers. A numerical study is executed to analyze the hole distributions in the quantum wells. From the simulated results, it is found that the hole injection efficiency can be improved at high injection current. Hence, the effective recombination of electron and hole is also enhanced at high injection current.
Improvement of defect reduction in semi-polar GaN grown on shallow-trenched Si(001) substrate
(2012)
Lee, Ling
;
Chien, Kun-Feng
;
Chou, Wu-Ching
;
Ko, Chih-Hsin
;
Wu, Cheng-Hsien
The improved design of sub-micron trenches on Si(001) substrate was demonstrated for defect suppression in semi-polar selectively-grown GaN layers. Cathodoluminescence and transmission electron microscopy measurements revealed a dramatically decreased density of threading dislocations and stacking faults near the surface of the overgrown GaN layer when the trench width ranged from 500 to 1500 nm. It was observed that defects were effectively trapped inside the trench when the ratio of trench depth to the SiO2 thickness is less than 0.66. In addition, a significant reduction of intrinsic polarization electric field was achieved for the InGaN/GaN multiple quantum well on the GaN selectively grown from the Si trenches.
Lifetime improvement of organic light emitting diodes using LiF thin film and UV glue encapsulation
(2008-07-01)
Huang, Jian-Ji
;
Su, Yan-Kuin
;
Chang, Ming-Hua
;
Hsieh, Tsung-Eong
;
Huang, Bohr-Ran
This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and preencapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivationlayer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.
Light emission characteristics of nonpolar a-plane GaN-based photonic crystal defect cavities
(2015-01-01)
Kao, Tsung Sheng
;
Wu, Tzeng-Tsong
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Tsao, Che-Wei
;
Lin, Jyun-Hao
;
Lin, Da-Wei
In this paper, nonpolar a-plane GaN-based photonic crystals (PCs) with different defect cavities have been demonstrated. By using a micro-photoluminescence (mu-PL) system operated at 77 K, the dominant resonant modes of the GaN-based PC defect cavities show high quality factor (Q) values in the light emission performance which can be up to 4.3x10(3). Moreover, the degree of polarization (DOP) of the light emission from the nonpolar GaN-based PC defect cavities was measured to achieve around 64 % along the m crystalline direction.
Light Emission Characteristics of Nonpolar a-Plane GaN-Based Photonic Crystal Defect Cavities
(2016-09)
Kao, Tsung Sheng
;
Wu, Tzeng-Tsong
;
Tsao, Che-Wei
;
Lin, Jyun-Hao
;
Lin, Da-Wei
In this paper, the light emission performance from nonpolar a-plane gallium nitride (GaN)-based photonic crystal (PC) slabs with line-type defect cavities has been investigated. Via the focused ion beam milling technique, thin membrane structures of the nonpolar GaN PC defect cavities were engineered, exhibiting one dominated resonant mode occurred at 419.3 nm with a high quality factor of 1.9 x 10(3) in the photoluminescence emission characterizations. In the far-field region, light emission performance shows a high polarization degree of 50% with the beam direction perpendicular to the defect cavity. Compared with the PC defect cavity patterns fabricated on c-axial oriented GaN materials, the a-plane PC defect cavities display not only the linear light output-input power dependence, but also an invariant resonant mode of constant light emission behavior with increasing the injection carriers, therefore providing a new perspective for the future development of promising optoelectronic devices.
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.
Low-Frequency Noise Performance of Al-Doped ZnO Nanorod Photosensors by a Low-Temperature Hydrothermal Method
(2017-08-01)
Wang, Zi-Hao
;
Yu, Hsin-Chieh
;
Yang, Chih-Chiang
;
Yeh, Hsin-Ting
;
Su, Yan-Kuin
In this paper, we developed a simple hydrothermal method to synthesize vertically aligned ZnO:Al nanorods (NRs) to fabricate a UV photodetector (PD) on a seed layer/glass substrate. The photo-to-dark current ratio of the ZnO: Al NR PD was approximately 1.4 x 10(3) under 1-V bias and UV light irradiation (380 nm). The calculated responsivity of the fabricated PD was 181 A . W-1, and the UV-to-visible rejection ratio of the PD at 1-V applied bias was 1.51 x 10(3). In addition, flicker noise dominated the noise of the ZnO: Al NR PD. The noise-equivalent power and normalized detectivity of the ZnO:Al NR PD were 1.17 x 10(-11) W and 4.03 x 10(12) cm . Hz(0.5)W(-1), respectively.
Optical Simulation and Fabrication of Near-Ultraviolet LEDs on a Roughened Backside GaN Substrate
(2012-03-15)
Fu, Yi-Keng
;
Lu, Yu-Hsuan
;
Xuan, Rong
;
Chao, Chia-Hsin
;
Su, Yan-Kuin
In this letter, the numerical and experimental demonstrations for enhancement of light extraction efficiency in near-ultraviolet light-emitting diodes (LEDs) with a roughened backside on the N-face surface of GaN substrate through a chemical wet-etching process are investigated. It was also found that the increased etching time can increase the height of hexagonal pyramids and decrease the density of hexagonal pyramids. With 20-mA injection current, it was found that forward voltages were 3.13 and 3.16 V while output powers were 13.15 and 27.18 mW for the conventional LED and roughened backside LED, respectively.
Optical Studies of GaAs Nanowires Grown on Trenched Si(001) Substrate by Cathodoluminescence
(2012-06-01)
Lee, Ling
;
Chien, Kun-Feng
;
Fan, Wen-Chung
;
Chou, Wu-Ching
;
Ko, Chih-Hsin
"The strains in GaAs nanowires, which were grown from 1700- to 80-nm-wide trenches on the Si(001) wafer with SiO2 masks, were investigated by cathodoluminescence. For 1700- to 500-nm-wide trenches, the in-plane tensile strain at 15 K decreases with the decreasing trench width. The strain increases abruptly when the trench width is 300 nm, and then decreases as the trench width is further decreased. The results revealed that the stress induced by the SiO2 sidewalls dominates when the width is less than the depth of the trench. This approach provides an effective technique to measure the strain of a single nanowire and helps for the demonstration of selectively-grown GaAs with a designed strain. (C) 2012 The Japan Society of Applied Physics"
Study of InGaN-Based Light-Emitting Diodes on a Roughened Backside GaN Substrate by a Chemical Wet-Etching Process
(2011-10-01)
Fu, Yi-Keng
;
Chen, Bo-Chun
;
Fang, Yen-Hsiang
;
Jiang, Ren-Hao
;
Lu, Yu-Hsuan
The InGaN-based light-emitting diodes (LEDs) with a roughened backside on the N-face surface of GaN substrate were fabricated through a chemical wet-etching process to increase light-extraction efficiency. The stable crystallographic etching planes were formed as the GaN {10 (11) over bar} planes. When the near-ultraviolet and blue LED were operated as a forward current of 20 mA, the output power of LEDs was improved from 13.2 and 19.9 mW to 25.6 and 24.0 mW, respectively. The different enhanced ratio is attributed to the different transmittance as a function of wavelength is caused from hexagonal pyramid on N-face GaN substrate after wet-etching process.
The Effect of Oxygen Vacancy Concentration on Indium Gallium Oxide Solar Blind Photodetector
(2018-05-01)
Chen, Kuan-Yu
;
Hsu, Ching-Chien
;
Yu, Hsin-Chieh
;
Peng, Yu-Ming
;
Yang, Chih-Chiang
In this paper, amorphous indium-gallium-oxide solar-blind metal-semiconductor-metal photodetectors were fabricated by using co-sputtering method. Three samples with different oxygen concentrations, namely, sample A without oxygen, sample B with 2% oxygen concentration, and sample C with 4% oxygen concentration, were investigated. The applied bias was 5 V during device characterization. The ultraviolet (UV)-to-visible rejection ratios were 39, 9.9 x 10(3), and 1.1 x 10(5) for samples A, B, and C, respectively. The dynamic responses of the decay times were 5.79/52.12 s, 1.96/30.49 s, and 0.02/0.75 s for samples A, B, and C, respectively. In summary, the 4% oxygen concentration sample exhibited excellent UV-to-visible rejection ratio and superior decay time.
The effect of trimethylgallium flows in the AIInGaN barrier on optoelectronic characteristics of near ultraviolet light-emitting diodes grown by atmospheric pressure metalorganic vapor phase epitaxy
(2011-03-21)
Fu, Yi-Keng
;
Jiang, Ren-Hao
;
Lu, Yu-Hsuan
;
Chen, Bo-Chun
;
Xuan, Rong
The letter reports a theoretical and experimental study on the device performance of near ultraviolet light-emitting diodes (LEDs) with quaternary AlInGaN quantum barrier (QB). The indium mole fraction of AlInGaN QB could be enhanced as we increased the trimethylgallium flow rate. It was found the AlInGaN/InGaN LEDs can reduce forward voltage and improve light output power, compared with conventional GaN QB. By using advanced device simulation, it should be attributed to a reduction in lattice mismatch induced polarization mismatch in the active layer, which results in the suppression of electron overflow. (C) 2011 American Institute of Physics. [doi:10.1063/1.3571440]