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Atomic Layer Epitaxy of Nitrogen-Doped ZnSe
TAKEMURA, YASUSHI,KONAGAI, MAKOTO,YAMASAKI, KANAME,LEE, C.H.,TAKAHASHI, KIYOSHI 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-
Atomic layer epitaxy of nitrogen-doped ZnSe was studied. The ZnSe films were grown on GaAs(001) substrates at 250℃ with a continuous flow of nitrogen and alternate supplies of zinc and selenium. The grown films were characterized by photoluminescence spectra at 4.2K, and it was found that nitrogen was incorporated as a shallow acceptor in the films. The Schottky diodes were prepared by evaporation gold on the nitrogen-doped films grown on p-type GaAs substrates. A rectifying characteristic that was consistent with the structure, assuming p-type conductivity of ZnSe, was observed. Catacitance-voltage measurement of the structure also indicated p-type conductivity of the films.
강동원,Porponth Sichanugrist,Makoto Konagai 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4
We successfully designed and experimentally demonstrated anapplication of patterned MgF2 dielectric material at rear Al-dopedZnO (AZO)/Ag interface in thin film amorphous silicon oxide (a-SiOx:H) solar cells. When it was realized in practical deviceprocess, MgF2 coverage with patterned morphology was employedto allow for current flow between the AZO and Ag against highlyresistive MgF2 material. On the basis of the suggested structure, wefound an improvement in quantum efficiency of the solar cells withthe patterned MgF2. In addition, an enhancement of open circuitvoltage (Voc) and fill factor (FF) was observed. A remarkableincrease in shunt resistance of the cells with the MgF2 wouldpossibly indicate that the highly resistive MgF2 layer can partlysuppress physical shunting across top and bottom electrodes causedby very thin absorber thickness of only 100 nm. The approachshowed that our best-performing device revealed an essentialimprovement in conversion efficiency from 7.83 to 8.01% withachieving markedly high Voc (1.013 V) and FF (0.729).
Taweewat Krajangsang,Ihsanul Afdi Yunaz,Shinsuke Miyajima,Makoto Konagai 한국물리학회 2010 Current Applied Physics Vol.10 No.3
A theoretical analysis using Analysis of Microelectronic and Photonic Structures (AMPS-1D) has been performed to investigate how the widegap p-lc-Si1-xOx:H influences the hetero-junction μc-Si:H solar cells. We observed that the open-circuit voltage (Voc) depends on the bandgap of p-layer. Using wide bandgap p-layer can reduce recombination at p-layer and p/i interface. Moreover, we also have studied the effect of light intensity on the performance of hetero-junction μc-Si:H solar cells. From simulation result, it was confirmed that the Voc logarithmically increases with increasing the light intensity. Besides, we also observed that the p-layer bandgap strongly influences the light-intensity dependence of hetero-junction μc-Si:H solar cells. The enhancement of Voc (DVoc) with increasing light intensity improves as the bandgap of p-layer is increased. Therefore, widegap p-μc-Si1-xOx:H is promising for use as window layer in hetero-junction μc-Si:H solar cells.
Dong-Won Kang,Jun Ryu,Makoto Konagai 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5
For low-cost and lightweight polymer/plastic substrates in flexible building-integrated photovoltaic (BIPV) modules, lowtemperatureprocessing is essential. Amorphous silicon (a-Si:H) requires processing at a temperature of 200–250 °C byplasma-enhanced chemical vapor deposition to obtain satisfactory optoelectronic properties, which limits such substratesin terms of thermal budget. This study is focused on the fabrication of p–i–n-type a-Si:H solar cells at relatively low temperatures(100 °C). Intrinsic a-Si:H films with large optical gaps (1.83 eV) were prepared at 100 °C using a high hydrogendilution ratio. In addition, p-type amorphous silicon oxide and n-type microcrystalline silicon oxide films with large opticalgaps and suitable conductivities were prepared at 100 °C using a gas mixture containing the dopant B2H6or PH3and CO2. Finally, an a-Si:H p–i–n cell was fabricated at 100 °C; it exhibited an excellent power conversion efficiency of 9.0%, whichwas higher than those reported for a-Si:H thin film photovoltaics prepared at 100 °C. We believe that this study will openpromising routes for the development of high-performance and flexible BIPVs.
Development of Wide Band Gap P-a-SiOxCy:H Using Additional Trimethylboron as Carbon Source Gas
강동원,Porponth Sichanugrist,Bancha Janthong,Muhammad Ajmal Khan,Chisato Niikura,Makoto Konagai 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4
We report p-type a-SiOxCy:H thin films which were fabricated byintroducing additional Trimethylboron (TMB, B(CH3)3) dopinggas into conventional standard p-type a-SiOx:H films. The TMBaddition into the condition of p-a-SiOx:H improved opticalbandgap from 2.14 to 2.20 eV without deterioration of electricalconductivity, which is promising for p-type window layer of thinfilm solar cells. The suggested p-a-SiOxCy:H films were appliedin amorphous silicon solar cells and we found an increase ofquantum efficiency at short wavelength regions due to widebandgap of the new p-layer, and thus efficiency improvementfrom 10.4 to 10.7% was demonstrated in a-Si:H solar cell byemploying the p-a-SiOxCy:H film. In case of a-SiOx:H cell, highopen circuit voltage of 1.01 V was confirmed by using thesuggested the p-a-SiOxCy:H film as a window layer. This new playercan be highly promising as a wide bandgap window layer toimprove the performance of thin film silicon solar cells.
Taweewat Krajangsang,Shunsuke Kasashima,Aswin Hongsingthong,Porponth Sichanugrist,Makoto Konagai 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Preparation of p-type hydrogenated microcrystalline silicon oxide thin films (p-mc-Si1-xOx:H) by 13.56 MHz RF-PECVD method for use as a p-layer of hetero-junction mc-Si:H solar cells is presented. We investigated effects of wide-gap p-mc-Si1-xOx:H layer on the performance of hetero-junction mc-Si:H solar cells under various light intensity. We observed that a wide-gap p-mc-Si1-xOx:H was effective in improving the open-circuit voltage (Voc) of the solar cells. We also confirmed that the Voc logarithmically increased with increasing light intensity, and the enhancement of Voc became larger with increasing band gap of p-layer. These results indicate that wide-gap p-mc-Si1-xOx:H is a promising material for use as window layer in hetero-junction mc-Si:H solar cells.
Development of a rapidly stabilized protocrystalline silicon multilayer solar cell
Myong, Seung Yeop,Kwon, Seong Won,Kondo, Michio,Konagai, Makoto,Lim, Koeng Su Institute of Physics 2006 Semiconductor science and technology Vol.21 No.2
<P>We develop a rapidly stabilized pin-type thin film solar cell with a low degradation by combining a p-type hydrogenated amorphous silicon-carbide (p-a-SiC:H) double layer structure and an alternately hydrogen-diluted protocrystalline silicon (pc-Si:H) multilayer absorber. The p-a-SiC:H double layer structure increases overall initial parameters by reducing recombination at the p/i interface. After 12 h standard light irradiation, we achieve a stabilized efficiency of 9.0% without using any back reflector. Nano-sized silicon grains embedded in regularly arranged highly hydrogen-diluted sublayers of the pc-Si:H multilayer suppress the photocreation of dangling bonds in a amorphous silicon matrix acting as radiative recombination centres of photoexcited carriers.</P>
Yasuyoshi Kurokawa,Shigeru Yamada,Shinsuke Miyajima,Akira Yamada,Makoto Konagai 한국물리학회 2010 Current Applied Physics Vol.10 No.3
It was found that the dark conductivity of a stoichiometric a-SiC thin film, which is used as barrier layers in a Si quantum dots superlattice (Si-QDSL), increased drastically after thermal annealing above 800 ℃. This is due to the crystallization of an a-SiC phase in the films. To resolve this problem, CO2gas was introduced during the deposition of stoichiometric a-SiC thin films. As a result, the dark conductivity of the films annealed at either 900 or 1000 ℃ was reduced below 10-9 S/cm, since the introduction of oxygen atoms into the films prevented the a-SiC phase from crystallizing during the annealing. O-containing Si-QDSLs were prepared and the dark conductivity of the O-containing Si-QDSLs was reduced in the range of 10-6–10-7 S/cm and increased with increasing the diameter of Si-QDs, suggesting that the leakage in barrier layers was suppressed and the carrier transport through Si-QDs became predominant.