Jae-Hyung Jang - Academia.edu (original) (raw)
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Papers by Jae-Hyung Jang
Journal of Nanoscience and Nanotechnology, 2011
Subwavelength structures (SWSs) were fabricated on the Indium Phosphide (InP) substrate by utiliz... more Subwavelength structures (SWSs) were fabricated on the Indium Phosphide (InP) substrate by utilizing the confined convective self-assembly (CCSA) method followed by reactive ion etching (RIE). The surface condition of the InP substrate was changed by depositing a 30-nm-thick SiO 2 layer and subsequently treating the surface with O 2 plasma to achieve better surface coverage. The surface coverage of nanoparticle monolayer reached 90% by using O 2 plasma-treated SiO 2 /InP substrate among three kinds of starting substrates such as the bare InP, SiO 2 /InP and O 2 plasma-treated SiO 2 /InP substrate. A nanoparticle monolayer consisting of polystyrene spheres with diameter of 300 nm was used as an etch mask for transferring a two-dimensional periodic pattern onto the InP substrate. The fabricated conical SWS with an aspect ratio of 1.25 on the O 2 plasma-treated SiO 2 /InP substrate exhibited the lowest reflectance. The average reflectance of the conical SWS was 5.84% in a spectral range between 200 and 900 nm under the normal incident angle.
Journal of Nanoscience and Nanotechnology, 2014
We have investigated THz radiation characteristics along different directions, either reflective ... more We have investigated THz radiation characteristics along different directions, either reflective or along lateral by using InAs-based heterostructures. Firstly, we demonstrate the phase shift with InAs layer thickness, revealing the change of dominant THz wave generation mechanism along both directions. Along the lateral direction, the time-domain signals in thin InAs epilayers showed an abrupt phase and amplitude change at certain time delays which suggest the interference between two rays at the photoconductive switch. This behavior was further substantiated by the multiple cavity modes in Fourier-transformed spectra and by the amplitude variation with excitation spot displacement.
IEEE Sensors Journal, 2000
We demonstrate a simple but sensitive hydrogen gas sensor composed of a palladium-coated long-per... more We demonstrate a simple but sensitive hydrogen gas sensor composed of a palladium-coated long-period fiber grating (LPG). By writing an LPG in a low core index fiber, high-order cladding modes are excited. As the palladium thin layer absorbs hydrogen, the effective refractive indexes of the cladding modes are affected, thus the resonant wavelengths of the LPG are changed with a high sensitivity. With 70-nm-thick coating, 7.5 nm of the hydrogen-induced spectral shift was achieved. The spectral response of the proposed sensor to hydrogen gas and its recovery with nitrogen gas are presented.
We report on room temperature Terahertz (THz) emission from a conventional single-gate Gallium Ni... more We report on room temperature Terahertz (THz) emission from a conventional single-gate Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) by virtue of Dyakonov-Shur plasma wave instability. The emission signal strength from the device was numerically integrated, and found to be 0.1 uW. The emission intensity was found to have a direct proportion with the applied drain bias. Non-resonant broad emission as well as resonant emission at 0.1 THz was observed at low and high drain bias respectively.
Journal of Nanoscience and Nanotechnology, 2011
Subwavelength structures (SWSs) were fabricated on the Indium Phosphide (InP) substrate by utiliz... more Subwavelength structures (SWSs) were fabricated on the Indium Phosphide (InP) substrate by utilizing the confined convective self-assembly (CCSA) method followed by reactive ion etching (RIE). The surface condition of the InP substrate was changed by depositing a 30-nm-thick SiO 2 layer and subsequently treating the surface with O 2 plasma to achieve better surface coverage. The surface coverage of nanoparticle monolayer reached 90% by using O 2 plasma-treated SiO 2 /InP substrate among three kinds of starting substrates such as the bare InP, SiO 2 /InP and O 2 plasma-treated SiO 2 /InP substrate. A nanoparticle monolayer consisting of polystyrene spheres with diameter of 300 nm was used as an etch mask for transferring a two-dimensional periodic pattern onto the InP substrate. The fabricated conical SWS with an aspect ratio of 1.25 on the O 2 plasma-treated SiO 2 /InP substrate exhibited the lowest reflectance. The average reflectance of the conical SWS was 5.84% in a spectral range between 200 and 900 nm under the normal incident angle.
Journal of Nanoscience and Nanotechnology, 2014
We have investigated THz radiation characteristics along different directions, either reflective ... more We have investigated THz radiation characteristics along different directions, either reflective or along lateral by using InAs-based heterostructures. Firstly, we demonstrate the phase shift with InAs layer thickness, revealing the change of dominant THz wave generation mechanism along both directions. Along the lateral direction, the time-domain signals in thin InAs epilayers showed an abrupt phase and amplitude change at certain time delays which suggest the interference between two rays at the photoconductive switch. This behavior was further substantiated by the multiple cavity modes in Fourier-transformed spectra and by the amplitude variation with excitation spot displacement.
IEEE Sensors Journal, 2000
We demonstrate a simple but sensitive hydrogen gas sensor composed of a palladium-coated long-per... more We demonstrate a simple but sensitive hydrogen gas sensor composed of a palladium-coated long-period fiber grating (LPG). By writing an LPG in a low core index fiber, high-order cladding modes are excited. As the palladium thin layer absorbs hydrogen, the effective refractive indexes of the cladding modes are affected, thus the resonant wavelengths of the LPG are changed with a high sensitivity. With 70-nm-thick coating, 7.5 nm of the hydrogen-induced spectral shift was achieved. The spectral response of the proposed sensor to hydrogen gas and its recovery with nitrogen gas are presented.
We report on room temperature Terahertz (THz) emission from a conventional single-gate Gallium Ni... more We report on room temperature Terahertz (THz) emission from a conventional single-gate Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) by virtue of Dyakonov-Shur plasma wave instability. The emission signal strength from the device was numerically integrated, and found to be 0.1 uW. The emission intensity was found to have a direct proportion with the applied drain bias. Non-resonant broad emission as well as resonant emission at 0.1 THz was observed at low and high drain bias respectively.