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Finite element analysis of antireflective silicon nitride sub-wavelength structures for solar cell applications
(2010-10-01)
Lee, Huang-Ming
;
Sahoo, Kartika Chandra
;
Li, Yiming
;
Wu, Jong-Ching
;
Chang, Edward Yi
We numerically calculate the spectral reflectivity of the silicon nitride (Si(3)N(4)) sub-wavelength structure (SWS) using a two-dimensional finite element simulation. The geometry-dependent effective reflectance of the Si(3)N(4) SWS over the wavelength ranging from 400 nm to 1000 nm is examined and the structure of Si(3)N(4) SWS is further optimized for the lowest effective reflectance. A p-n junction solar cell efficiency based on the optimized Si(3)N(4) SWS is also calculated, resulting in an improvement of 0.98% in efficiency than that of single layer antireflection coatings. (C) 2010 Elsevier B.V. All rights reserved.
Shape Effect of Silicon Nitride Subwavelength Structure on Reflectance for Silicon Solar Cells
(2010-10-01)
Sahoo, Kartika Chandra
;
Li, Yiming
;
Chang, Edward Yi
;
材料科學與工程學系
;
電機工程學系
In this paper, we, for the first time, examine the spectral reflectivity of hemisphere-, cone-, cylinder-, and parabola-shaped silicon nitride (Si(3)N(4)) subwavelength structures (SWSs). A multilayer rigorous coupled-wave approach is advanced to evaluate the reflection properties of Si(3)N(4) SWSs. We optimize the aforementioned four different shapes of SWSs in terms of effective reflectance over a range of wavelength. The results of our paper show that a lowest effective reflectivity could be achieved for the optimized cone-shaped SWS as compared to hemisphere-, parabola-, and cylinder-shaped structures with the same volume. The best shape SWS is then fabricated together with a silicon (Si) solar cell, and the efficiency of the solar cell is compared with that of a solar cell with single-layer antireflection coating (ARC). An increase of 1.09% in cell efficiency (eta) is observed for the Si solar cell with a cone-shaped Si(3)N(4) SWS (eta = 12.86%) as compared with the cell with single-layer Si(3)N(4) ARCs (eta = 11.77%).
Novel Metamorphic HEMTs With Highly Doped InGaAs Source/Drain Regions for High Frequency Applications
(2010-10-01)
Sahoo, Kartika Chandra
;
Kuo, Chien-I
;
Li, Yiming
;
Chang, Edward Yi
;
傳播研究所
In this paper, we report the first result of a strained In(0.52)Ga(0.48) As channel high-electron mobility transistor (HEMT) featuring highly doped In(0.4)Ga(0.6) As source/drain (S/D) regions. A lattice mismatch of 0.9% between In(0.52)Ga(0.48) As and In(0.4)Ga(0.6) As S/D has resulted in a lateral strain in the In(0.52)Ga(0.48) As channel region, where the series resistance is reduced with highly doped S/D regions. An experimentally validated device simulation is advanced for the proposed HEMT, and the results of this paper have shown that there are 60% drive-current and 100% transconductance improvements, compared with the conventional structure. A remarkable 150-GHz increase in the cutoff frequency has been seen for the proposed structure over the conventional one as well for the shown devices.
Fabrication and characterization of n-In0.4Ga0.6N/p-Si solar cell
(2012-07-01)
Tran, Binh-Tinh
;
Chang, Edward-Yi
;
Trinh, Hai-Dang
;
Lee, Ching-Ting
;
Sahoo, Kartika Chandra
Electro-optic characteristics of a fabricated n-In0.4Ga0.6N/p-Si hetero-structure solar cell on Si substrate with Al and ITO (or Ti/Al/Ni/Au) materials for p and n-type contacts were investigated in this letter. The solar cell devices with ITO as n-type contacts were also compared to the solar cell using Ti/Al/Ni/Au as n-type contact in this study. High short-circuit current density observed for solar cell with ITO as n-type contacts due to the increased amount of light reaching the solar cell. The device with ITO contact exhibited an open-circuit voltage (V-oc) of 1.52 V and a short-circuit current density (J(sc)) of 8.68 mA/cm(2) with 54% fill factor. The conversion and external quantum efficiency (EQE) of the solar cell were 7.12 and 20.8%, respectively. Besides, a relationship between V-oc and In content in the InxGa1-xN alloys for this type of solar cell was also derived. (C) 2012 Elsevier B.V. All rights reserved.
Novel Cu/Cr/Ge/Pd ohmic contacts on highly doped n-GaAs
(2008-06-01)
Sahoo, Kartika Chandra
;
Chang, Chun-Wei
;
Wong, Yuen-Yee
;
Hsieh, Tung-Ling
;
Chang, Edward Yi
The thermal stability of the Cu/Cr/Ge/Pd/n(+)-GaAs contact structure was evaluated. In this structure, a thin 40 nm layer of chromium was deposited as a diffusion barrier to block copper diffusion into GaAs. After thermal annealing at 350 degrees C, the specific contact resistance of the copper-based ohmic contact Cu/Cr/Ge/Pd was measured to be (5.1 +/- 0.6) x 10(-7) Omega cm(2). Diffusion behaviors of these films at different annealing temperatures were characterized by metal sheet resistance, X-ray diffraction data, Auger electron spectroscopy, and transmission electron microscopy. The Cu/Cr/Ge/Pd contact structure was very stable after 350 degrees C annealing. However, after 400 degrees C annealing, the reaction of copper with the underlying layers started to occur and formed Cu3Ga, Cu3As, Cu9Ga4, and Ge3Cu phases due to interfacial instability and copper diffusion.
Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application
(2009-07-01)
Sahoo, Kartika Chandra
;
Lin, Men-Ku
;
Chang, Edward-Yi
;
Lu, Yi-Yao
;
Chen, Chun-Chi
We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160-200 nm and a height of 140-150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen.
Numerical calculation of the reflectance of sub-wavelength structures on silicon nitride for solar cell application
(2009-10-01)
Sahoo, Kartika Chandra
;
Li, Yiming
;
Chang, Edward Yi
;
材料科學與工程學系
;
電子工程學系及電子研究所
In this study, we calculate the spectral reflectivity of pyramid-shaped silicon nitride (Si(3)N(4)) sub-wavelength structures (SWS). A multilayer rigorous coupled-wave approach is advanced to investigate the reflection properties of Si(3)N(4) SWS. We examine the simulation results for single layer antireflection (SLAR) and double layer antireflection (DLAR) coatings with SWS on Si(3)N(4) surface, taking into account effective reflectivity over a range of wavelengths and solar efficiency. The results Of Our study show that a lowest effective reflectivity of 1.77% can be obtained for the examined Si(3)N(4) SWS with the height of etched part of Si(3)N(4) and the thickness of non-etched layer of 150 and 70 rim, respectively, which is less than the results of an optimized 80 nm Si(3)N(4) SLAR (similar to 5.41%) and of an optimized DLAR with 80 nm Si(3)N(4) and 100 nm magnesium fluoride (similar to 5.39%). 1% cell efficiency increase is observed for the optimized Si solar cell with Si(3)N(4) SWS, compared with the cell with single layer Si(3)N(4) antireflection coatings (ARCs); furthermore, compared with DLAR coated solar cell, the increase is about 0.71%. The improvement on the cell efficiency is mainly due to lower reflectance Of Si(3)N(4) SWS over a wavelength region from 400 to 600 nm that leads to lower short circuit current. (C) 2009 Elsevier B.V. All rights reserved.
Silicon Nitride Nanopillars and Nanocones Formed by Nickel Nanoclusters and Inductively Coupled Plasma Etching for Solar Cell Application
(2009-12-01)
Sahoo, Kartika Chandra
;
Lin, Men-Ku
;
Chang, Edward-Yi
;
Tinh, Tran Binh
;
Li, Yiming
The external quantum efficiency of solar cells can be improved by using textured surface with minimum reflection. We have fabricated nanopillars and nanocone structures on silicon nitride surface by means of self-assembled nickel nano particle masks with single step inductively coupled plasma (ICP) ion etching and double step ICP etching, respectively. Thus, sub-wavelength nanopillar and nanocone-like structures displaying low reflectance were obtained readily without the need for any lithography equipment. The formation mechanism of nanopillar and nanocone like structures fabricated on silicon nitride surface has been discussed. The relationship of etching time with structure height and average reflectance spectra has been drawn. (C) 2009 The Japan Society of Applied Physics

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