Suigen, South Korea
Suigen, South Korea

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Cho Y.,Ewha Womans University | Gwon M.,Ewha Womans University | Park H.-H.,Korea Advanced Nano Fab Center | Kim J.,Incheon National University | Kim D.-W.,Ewha Womans University
Nanoscale | Year: 2014

A high photocurrent of 36.96 mA cm-2 was achieved for wafer-scaled crystalline Si solar cells with hexagonal nanoconical frustum arrays at the surface. Optical simulations showed that the expected photocurrent of 10 μm thick nanostructured cells could slightly exceed the Lambertian limit. © 2014 the Partner Organisations.

Leem J.W.,Kyung Hee University | Yu J.S.,Kyung Hee University | Heo J.,Korea Advanced Nano Fab Center | Park W.-K.,Korea Advanced Nano Fab Center | And 3 more authors.
Solar Energy Materials and Solar Cells | Year: 2014

We report the effect of nanocone arrays (NCAs) as an antireflection coating (ARC) of encapsulation coverglasses on the device performance of encapsulated III-V InGaP/GaAs/Ge triple-junction (TJ) solar cells. The NCAs were fabricated on the single-side surface of glasses using the gold nanopatterns (i.e., nanoclusters) prepared by the glancing angle deposition technique without additional thermal treatment and the subsequent dry etching. Their wetting behavior and optical properties, together with a theoretical prediction using the rigorous coupled-wave analysis method, were investigated. The NCAs ARC coverglass exhibited a much lower water contact angle (θCA) of <5 (i.e., superhydrophilic surface) and higher solar weighted transmittance (SWT) of ~95.9% over a wide wavelength region of 300-1800 nm at normal incidence compared to the bare coverglass (i.e., θCA~63 and SWT ~92.8%). The use of the NCAs ARC coverglass in encapsulated III-V InGaP/GaAs/Ge TJ solar cells led to the higher short circuit current density (Jsc) of 14.22 mA/cm2 and thus improved the conversion efficiency (η) to 32.07% (cf., Jsc=13.84 mA/cm2 and η=30.6% for the cell with the bare coverglass). For incident angle-dependent solar cell characteristics, it also showed a superior solar power conversion property in wide incident light angles of 20-80. © 2013 Elsevier B.V.

Hong S.-H.,Incheon National University | Yun J.-H.,State University of New York at Buffalo | Park H.-H.,Korea Advanced Nano Fab Center | Kim J.,Incheon National University
Applied Physics Letters | Year: 2013

An effective light-managing structure has been achieved by using a nano-imprint method. A transparent conductor of indium-tin-oxide (ITO) was periodically nanodome-shaped to have a height of 200 nm with a diameter of 340 nm on a p-type Si substrate. This spontaneously formed a heterojunction between the ITO layer and Si substrate and effectively reduced the light-reflection. The ITO nanodome device response was significantly enhanced to 6010 from the value of 72.9 of a planar ITO film. The transparent conducting ITO nanodome structure efficiently manipulates the incident light driving into the light-absorber and can be applied in various photoelectric applications. © 2013 AIP Publishing LLC.

Patel M.,Incheon National University | Kim H.-S.,Incheon National University | Park H.-H.,Korea Advanced Nano Fab Center | Kim J.,Incheon National University
Applied Physics Letters | Year: 2016

Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W-1) and detectivity (2.75 × 1015 Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells. © 2016 AIP Publishing LLC.

Song K.M.,Korea Advanced Nano Fab Center | Kim H.,Hanbat National University
Japanese Journal of Applied Physics | Year: 2012

The optical properties of undoped a-plane GaN films grown by metal organic vapor phase epitaxy (MOVPE) with different initial growth pressures were investigated using photoluminescence (PL) measurements. Compared to GaN sample grown with higher initial grown pressure, which exhibited the dominant emission band at 3.423 eV, the dominant PL spectra for GaN sample grown with lower initial growth pressure was the donor-acceptor pair (DAP) band at 3.268 eV. Interestingly, the PL intensity of DAP longitudinal optical (LO) phonon replica was stronger than DAP emission above 50 K, indicating strong phonon coupling. The emission band at 3.359 eV observed for the sample grown with higher initial growth pressure was not observed for the sample grown with lower initial growth pressure. Based on the results obtained from Si doping, it was suggested that this band might be related with the improved crystalline quality through Si doping. © 2012 The Japan Society of Applied Physics.

Cho C.-Y.,Korea Advanced Nano Fab Center | Park S.-J.,Gwangju Institute of Science and Technology
Optics Express | Year: 2016

We report the optical properties of localized surface plasmon (LSP)-enhanced green light-emitting diodes (LEDs) containing gold (Au) nanoparticles embedded in a p-GaN layer. The photoluminescence (PL) and electroluminescence (EL) intensities of a green LED with Au nanoparticles were enhanced by the coupling between excitons and LSPs. Excitation power-dependent PL and injection current-dependent EL measurements revealed that the blue-shift of PL and EL peaks with increasing carrier density was smaller for the LSP-enhanced LED compared with that for a conventional LED. The increased optical output power and decrease in blue-shift of the LED with Au nanoparticles were attributed to the increased radiative recombination efficiency of carriers induced by the LSP-coupling process and the compensation of the polarization-induced electric fields with LSP-enhanced local fields, both of which suppressed the quantumconfined Stark effect. © 2016 Optical Society of America.

Leem J.W.,Kyung Hee University | Su Yu J.,Kyung Hee University | Jun D.-H.,Korea Advanced Nano Fab Center | Heo J.,Korea Advanced Nano Fab Center | Park W.-K.,Korea Advanced Nano Fab Center
Solar Energy Materials and Solar Cells | Year: 2014

The power conversion efficiency (PCE) improvement of III-V gallium arsenide (GaAs) single-junction (SJ) solar cells with titanium dioxide (TiO2) subwavelength structures (SWSs) as antireflection coatings (ARCs) is reported. TiO2 SWSs are fabricated by dry etching using dotted gold nanopatterns prepared with glancing angle deposition and thermal dewetting processes. Their optical reflection properties are studied in the wavelength range of 350-900 nm at incident light angles (θi) of 3-80°, together with the theoretical prediction by a rigorous coupled-wave analysis. For SWSs on the 50 nm-thick TiO2 layer/GaAs substrate, a lower solar weighted reflectance (SWR) of ~6.2% is obtained compared to that (i.e., SWR ~9.5%) of the TiO2 single-layer ARC (SLARC). By employing the TiO2 SWSs into the III-V GaAs SJ solar cell, the increased short circuit current density (Jsc) of 24.82 mA/cm2 is achieved, thus leading to an improved PCE of 19.66% at θi=0° (i.e., Jsc=18.38 and 23.65 mA/cm2 and PCE=14.74 and 18.98% for the solar cells with bare surface and TiO2 SLARC, respectively). For incident angle-dependent device characteristics, the solar cell with the TiO2 SWSs also exhibits superior performance over a wide θi range of 20-80°. Additionally, after the encapsulation, its Jsc and PCE values are slightly increased to 26.15 mA/cm 2 and 20.73%, respectively. For the stability, there are no significant variations in Jsc and PCE after about 50 days. © 2014 Elsevier B.V.

Kim H.,Seoul National University of Science and Technology | Song K.M.,Korea Advanced Nano Fab Center
Journal of Luminescence | Year: 2014

The temperature-dependent optical characteristics of blue luminescence (BL) band in Mg-doped nonpolar a-plane GaN films were investigated using photoluminescence (PL) measurements. For the sample with the highest Cp 2Mg/TMGa ([Mg]/[Ga]) molar ratio, the BL band was shown to have two distinct peaks, one at about 2.95 eV and the other at about 2.75 eV, which were associated with the donor-acceptor pair (DAP) transitions between the one shallow Mg acceptor level and the two different deep donor levels. In contrast, a single broad BL band was observed for all other samples. Strong potential fluctuations caused by high compensation level in the sample with the highest [Mg]/[Ga] molar ratio might localize the carriers related to the 2.75 eV band, leading to the different emission characteristics in BL band as compared to other samples. © 2013 Elsevier B.V.

Choi Y.,Chonbuk National University | Man Song K.,Korea Advanced Nano Fab Center | Kim H.,Chonbuk National University
Applied Physics Letters | Year: 2012

We investigated the Schottky barrier height and S-parameter at nonpolar (11-20) a-plane p-GaN surfaces by using Schottky diodes fabricated with various metals, including Ti, Cu, Ni, and Pt. A barrier inhomogeneity model was used to explain anomalous carrier transport behavior at the nonpolar p-GaN surfaces, yielding the mean barrier heights of 2.01, 1.73, 1.82, and 1.92eV for the Ti, Cu, Ni, and Pt contacts, respectively. The extracted S-parameter was as low as 0.02, indicating perfect pinning of the surface Fermi level at around 1.9eV above the valence band. © 2012 American Institute of Physics.

Korea Advanced Nano Fab Center | Date: 2013-11-21

This invention relates to a method of healing defects at junctions of a semiconductor device, which includes growing a p-Ge layer on a substrate, performing ion implantation on the p-Ge layer to form an n+ Ge region or performing in-situ doping on the p-Ge layer and then etching to form an n+ Ge region or depositing an oxide film on the p-Ge layer and performing patterning, etching and in-situ doping to form an n+ Ge layer, forming a capping oxide film, performing annealing at 600700 C. for 13 hr, and depositing an electrode, and in which annealing enables Ge defects at n+/p junctions to be healed and the depth of junctions to be comparatively reduced, thus minimizing leakage current, thereby improving properties of the semiconductor device and achieving high integration and fineness of the semiconductor device.

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