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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.


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.


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.


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.

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