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Kikuo Makita – One of the best experts on this subject based on the ideXlab platform.

  • Theoretical and Experimental Study on Waveguide Avalanche Photodiodes With an Undepleted Absorption Layer for 25-Gb/s Operation
    Journal of Lightwave Technology, 2011
    Co-Authors: Kazuhiro Shiba, T. Nakata, T. Takeuchi, K. Kasahara, Kikuo Makita

    Abstract:

    Waveguide avalanche photodiodes (WG-APDs) have been developed for a 25-Gb/s operation. The waveguide structure was adopted for the APDs in order to achieve both high-speed performance and high responsivity. First, the dependence of the multiplication and Absorption Layer thickness on the 3-dB bandwidths of the WG-APDs was theoretically clarified. It was found that introducing an undepleted Absorption Layer was effective in improving the 3-dB bandwidth without reducing efficiency. The 3-dB bandwidth of the fabricated WG-APD based on the calculation results was over 20 GHz up to a multiplication factor of 7. The responsivities were 0.6 A/W for 1.31 m and 0.75 A/W for 1.55 m wavelength. High reliability of the WG-APDs was also demonstrated.

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  • 40 Gbit=s waveguide avalanche photodiode with p-type Absorption Layer and thin InAlAs multiplication Layer
    Electronics Letters, 2007
    Co-Authors: Sho Shimizu, Kazuhiro Shiba, T. Nakata, K. Kasahara, Kikuo Makita

    Abstract:

    Waveguide avalanche photodiodes exhibiting both wide bandwidth and high gain bandwidth product have been developed. An Absorption Layer includes a p-type quasi-field-formed Layer and a multiplication Layer consists of InAlAs with a low ionisation rate ratio. Optimisation of the design yielded superior performance such as a wide bandwidth of 36.5 GHz, a gain band width of 170 GHz and a high quantum efficiency of 0.75 A/W.

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Cheul-ro Lee – One of the best experts on this subject based on the ideXlab platform.

  • Se interLayer in CIGS Absorption Layer for solar cell devices
    Journal of Alloys and Compounds, 2015
    Co-Authors: Seung-kyu Lee, Jae-kwan Sim, N. J. Suthan Kissinger, Il-seok Song, Jin Soo Kim, Byung-joon Baek, Cheul-ro Lee

    Abstract:

    Abstract A CIGS absorber Layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage Voc. Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS Absorption Layer would be controlled. In order to reduce Se vacancy and confirm Ga inter-diffusion, two CIGS solar cells were fabricated by converting CIG precursor with and without Se interLayer. The copper-indium metallic precursors were fabricated corresponding to the sequence CuIn/In/Mo/STS on stainless steel (STS) substrates by sequential direct current magnetron sputtering while Se Layer was evaporated by rapid thermal annealing (RTA) system to obtain a Se/CuIn/In/Mo/STS stack. CuGa precursor Layer was also fabricated on the Se/CuIn/In/Mo/STS stack. Finally, both CuGa/Se/CuIn/In/Mo/STS and CuGa/CuIn/In/Mo/STS stacks were selenized at 500 °C for 1 h. It was clearly observed from the secondary ion mass spectroscopy (SIMS) and X-ray diffraction (XRD) that there was a change between the fabricated CIGS Absorption Layers and the amount of Ga elements. Furthermore, the Ga elements gradually decreased from the top to the bottom Layer of the CIGS Absorption Layer. We also discussed the effect of Se interLayer in the CIGS Absorption Layer and its influence on the solar cell’s performance.

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  • Development of gold induced surface plasmon enhanced CIGS Absorption Layer on polyimide substrate
    Applied Surface Science, 2013
    Co-Authors: Seong-un Park, Jae-kwan Sim, Jin Soo Kim, Byung-joon Baek, Rahul Sharma, Haeng-kwun Ahn, Cheul-ro Lee

    Abstract:

    Abstract Localized surface plasmon resonance (LSPR) with metal nanoparticles is the promising phenomenon to increase light Absorption by trapping light in thin film solar cells. In this study we demonstrate a successful LSPR effect with gold (Au) nanoparticles onto the Cu(In,Ga)Se 2 (CIGS) Absorption Layer. First, the CIGS absorber Layers is fabricated onto the Mo coated polyimide (PI) substrate by using two stage process as DC sputtering of CIG thin film followed by the selenization at 400 °C. Finally, the Au nanoparticles are deposited onto the CIGS Layer with increasing particles size from 4–15 nm by using sputter coater for 10–120 s. The X-ray diffraction (XRD) patterns confirm the formation of CIGS/Au nanocomposite structure with prominent peak shift of CIGS reflections and increasing intensity for Au phase. The CIGS/Au nanocomposite morphologies with Au particle size distribution uniformity and surface coverage is examined under ultra-high resolution field effect scanning electron microscope (UHR-FESEM). A peak at 176 cm −1 in Raman spectra, associated with the “A1” mode of lattice vibration for the attributed to the pure chalcopyrite structure. The secondary ion mass spectroscopy (SIMS) showed ∼200 nm depth converge of Au nanoparticles into the CIGS Absorption Layer. The optical properties as transmittance, reflectance and absorbance of CIGS/Au Layers were found to expand in the infrared region and the LSPR effect is the most prominent for Au particles (5–7 nm) deposited for 60 s. The Absorption coefficient and band gap measurement also confirms that the LSPR effect for 5–7 nm Au particles with band gap improvement from 1.31 to 1.52 eV for CIGS/Au Layer as the defect density decreases due to the deposition of Au nanoparticles onto the CIGS Layer. Such LSPR effect in CIGS/Au nanocomposite Absorption Layer will be a key parameter to further improve performance of the solar cell.

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  • Band gap engineering of tandem structured CIGS compound Absorption Layer fabricated by sputtering and selenization
    Journal of Alloys and Compounds, 2013
    Co-Authors: San Kang, Rahul Sharma, Jae-kwan Sim, Cheul-ro Lee

    Abstract:

    Abstract Band gap engineering was executed to fabricate a multi-junction stacked i.e. tandem Cu(In,Ga)Se 2 (CIGS) Absorption Layer. The CIGS Absorption Layers consist of multi-junction stacked CIS/CIGS/CGS thin films from bottom to top with increasing band gap. Tandem CIGS Layers were fabricated by using three precursor of CuIn, In/CuGa/In, and CuGa onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuIn, CuGa, and In targets. The CIG precursors were converted into CIGS Absorption thin film by selenization process. From the X-ray diffraction (XRD) pattern of CIS/CIGS/CGS tandem Layer, with the prominent peak shift for (1 1 2) reflections was attributed to the individual CIS, CIGS, and CGS phases at 26.76°, 27.15°, and 27.65° diffraction angles, respectively. The morphologies and atomic (at%) composition uniformity onto the surface and along the depth were extensively analyzed with field effect scanning electron microscope (FESEM) attached energy dispersive spectroscopy (EDS) and secondary ion mass spectroscopy (SIMS). The optical properties such as transmittance, reflectance and absorbance were found to improve in the infrared region for all the tandem CIGS Layers. Near the fundamental Absorption edge, the Absorption coefficient was approached to 10 5  cm −1 for CIS/CIGS/CGS tandem Layer. The straight-line behavior indicates that the films have a direct band gap. The band gap was found to increase from 1.15 to 1.74 eV with the Ga-grading along the depth of individual CIS, CIGS, and CGS thin films. In the tandem CIGS Layer, consist of CIS/CIGS, CIS/CGS, and CIS/CIGS/CGS thin films, the band gap was further increased from 1.42 to 2.06 eV, respectively. Such band gap engineering in CIGS tandem Absorption Layer will be a stepping stone to further improve the solar cell performance.

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Kazuhiro Shiba – One of the best experts on this subject based on the ideXlab platform.

  • Theoretical and Experimental Study on Waveguide Avalanche Photodiodes With an Undepleted Absorption Layer for 25-Gb/s Operation
    Journal of Lightwave Technology, 2011
    Co-Authors: Kazuhiro Shiba, T. Nakata, T. Takeuchi, K. Kasahara, Kikuo Makita

    Abstract:

    Waveguide avalanche photodiodes (WG-APDs) have been developed for a 25-Gb/s operation. The waveguide structure was adopted for the APDs in order to achieve both high-speed performance and high responsivity. First, the dependence of the multiplication and Absorption Layer thickness on the 3-dB bandwidths of the WG-APDs was theoretically clarified. It was found that introducing an undepleted Absorption Layer was effective in improving the 3-dB bandwidth without reducing efficiency. The 3-dB bandwidth of the fabricated WG-APD based on the calculation results was over 20 GHz up to a multiplication factor of 7. The responsivities were 0.6 A/W for 1.31 m and 0.75 A/W for 1.55 m wavelength. High reliability of the WG-APDs was also demonstrated.

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  • 40 gbit s waveguide avalanche photodiode with p type Absorption Layer and thin inalas multiplication Layer
    Electronics Letters, 2007
    Co-Authors: Sho Shimizu, Kazuhiro Shiba, T. Nakata, K. Kasahara, K Makita

    Abstract:

    Waveguide avalanche photodiodes exhibiting both wide bandwidth and high gain bandwidth product have been developed. An Absorption Layer includes a p-type quasi-field-formed Layer and a multiplication Layer consists of InAlAs with a low ionisation rate ratio. Optimisation of the design yielded superior performance such as a wide bandwidth of 36.5 GHz, a gain band width of 170 GHz and a high quantum efficiency of 0.75 A/W.

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  • 40 Gbit=s waveguide avalanche photodiode with p-type Absorption Layer and thin InAlAs multiplication Layer
    Electronics Letters, 2007
    Co-Authors: Sho Shimizu, Kazuhiro Shiba, T. Nakata, K. Kasahara, Kikuo Makita

    Abstract:

    Waveguide avalanche photodiodes exhibiting both wide bandwidth and high gain bandwidth product have been developed. An Absorption Layer includes a p-type quasi-field-formed Layer and a multiplication Layer consists of InAlAs with a low ionisation rate ratio. Optimisation of the design yielded superior performance such as a wide bandwidth of 36.5 GHz, a gain band width of 170 GHz and a high quantum efficiency of 0.75 A/W.

    Free Register to Access Article