Browsing by Author "Yeh, Yu-Hsiang"

Now showing 1 - 5 of 5

Efficiency evaluation of a hybrid miniaturized concentrated photovoltaic for harvesting direct/diffused solar light
(2019-03-01)
Tsao, Wei-Chen
;
Zeng, Qiu-Chun
;
Yeh, Yu-Hsiang
;
Tsai, Chih-Hung
;
Hong, Hwen-Fen
In this paper, a miniaturized concentrator photovoltaic (CPV) system is experimentally demonstrated based on a hot embossing silicone lens array with a size of 2 cm x 2 cm. Owing to the small size of the lens array, the total track of the CPV system can be as small as 4 cm. Consequently, the weight of the CPV system can be much lower than conventional bulky CPV system. For harvesting the diffuse solar radiation, perovskite solar cells are mounted adjacent to a multi junction solar cell. Theoretically, the short-circuit current of the CPV system can be enhanced from 48.1 to 85.5 mA for gamma = 0.7. The enhancement can be much higher for off-normal incident light. This kind of hybrid CPV system will be useful for cloudy weather and also useful for compensating the loss caused by the miss-alignment of the tracking module.
Improved Output Power of InGaN LEDs by Lateral Overgrowth on Si-Implanted n-GaN Surface to Form Air Gaps
(2012-08-01)
Tu, Shang-Ju
;
Lee, Ming-Lun
;
Yeh, Yu-Hsiang
;
Huang, Feng-Wen
;
Chen, Po-Cheng
"In this paper, air gaps were embedded in the n-GaN layer to improve light output power of InGaN-based light-emitting diodes (LEDs). Si ions (Si+28) were implanted on the n-GaN surface, causing a lattice constant disorder. Therefore, the GaN grown on the Si-implanted areas had a lower growth rate than the implantation-free regions. Without using a dielectric thin film, lateral epitaxial overgrowth technique was used to form air gaps above the implanted regions and below the active layers of InGaN LEDs. We proposed the growth mechanisms of GaN layer on the Si-implanted GaN templates and characterized the InGaN-based LEDs with embedded air gaps array. With a 20-mA current injection, experimental results indicate that light output power (LOP) of the proposed LEDs was enhanced by 36%, compared with those of the conventional LEDs. This enhancement can be attributed to the light scattering at the textured GaN/gap interfaces to increase the effective light escape cone in the LEDs. Based on ray tracing simulation, if the height and the width of bottom of gaps were increased to 3 mu m, the Lop could be enhanced over 70%."
Improved Power Conversion Efficiency of InGaN Photovoltaic Devices Grown on Patterned Sapphire Substrates
(2011-04-01)
Yang, C. C.
;
Sheu, J. K.
;
Kuo, C. H.
;
Huang, M. S.
;
Tu, S. J.
The InGaN/sapphire-based photovoltaic (PV) cells with Al(0.14)Ga(0.86)N/In(0.21)Ga(0.79)N superlattice structures that serve as absorption layers were grown on patterned sapphire substrates (PSSs). Under global air-mass 1.5 conditions, the short-circuit current density, the open-circuit voltage, and the fill factor obtained from the PV cells were 1.21 mA/cm(2), 2.18 V, and 0.65, respectively, corresponding to a conversion efficiency of 1.71%. Compared with PV devices grown on flat sapphire substrates, the photocurrent of PSS-grown PV devices was enhanced by 26%. The improved PV performance was attributable to the positive effects of the PSS on the material quality.
Optical properties of Mn in regrown GaN-based epitaxial layers
(2012-04-01)
Huang, Feng-Wen
;
Sheu, Jinn-Kong
;
Tu, Shang-Ju
;
Chen, Po-Cheng
;
Yeh, Yu-Hsiang
The memory effect and redistribution of manganese (Mn) into subsequently regrown GaN-based epitaxial layers by metalorganic chemical vapor deposition were revealed. Low-temperature up-converted photoluminescence (UPL) and the secondary ion mass spectrometry were performed on GaN-based epitaxial samples with and without Mn doping to study the effect of residual Mn on optical property. UPL emission, which originated from residual Mn doping in regrown InGaN quantum wells (QWs) because of the memory effect of the reactor, could be eliminated in an air-exposed and H-2-baking manner prior to the regrowth of the QWs. Considerable residual Mn background level and slow decay rate of Mn concentration tail were also observed in the regrown epitaxial layers, which could be attributed to the memory effect or surface segregation and diffusion from the Mn-doped underlying layer during regrowth in the Mn-free reactor. (C) 2012 Optical Society of America
Structual Design of T-gate, Air-spacer Poly-Si TFTs for RF applications
(2019-01-01)
Huang, Yu-An
;
Yeh, Yu-Hsiang
;
Lin, Horng-Chih
;
Li, Pei-Wen
;
電子工程學系及電子研究所
We employed Sentaurus TCAD simulation to explore the impacts of major structural parameters on the electrical characteristics of poly-Si TFTs with T-gate and air spacers. The effects and trade-off between the source/drain (S/D) junctions relative to T-gate are discussed with the aim to find insightful information for the design and fabrication of real devices. Influences of the gate geometry on the parasitic capacitances of the T-gate devices are also simulated.