http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Single n-GaN microwire/p-Silicon thin film heterojunction light-emitting diode.
Ahn, Jaehui,Mastro, Michael A,Klein, Paul B,Hite, Jennifer K,Feigelson, Boris,Eddy, Charles R,Kim, Jihyun Optical Society of America 2011 Optics express Vol.19 No.22
<P>The emission and waveguiding properties of individual GaN microwires as well as devices based on an n-GaN microwire/p-Si (100) junction were studied for relevance in optoelectronics and optical circuits. Pulsed photoluminescence of the GaN microwire excited in the transverse or longitudinal direction demonstrated gain. These n-type GaN microwires were positioned mechanically or by dielectrophoretic force onto pre-patterned electrodes on a p-type Si (100) substrate. Electroluminescence from this p-n point junction was characteristic of a heterostructure light-emitting diode. Additionally, waveguiding was observed along the length of the microwire for light originating from photoluminescence as well as from electroluminescence generated at the p-n junction.</P>
Nanostructured n-ZnO / thin film p-silicon heterojunction light-emitting diodes.
Ahn, Jaehui,Park, Hyunik,Mastro, Michael A,Hite, Jennifer K,Eddy, Charles R,Kim, Jihyun Optical Society of America 2011 Optics express Vol.19 No.27
<P>Electroluminescence (EL) was obtained from a p-Si (100) thin film/nanostructured n-ZnO heterojunction diode fabricated by a simple dielectrophoresis (DEP) method. The Si substrate was pre-patterned with electrodes and an insulating separation layer by a standard photolithographic process. ZnO nanostructures were formed by a simple solution chemistry and subsequently transferred to the pre-patterned substrate. Application of the DEP force at a frequency of 100 kHz and 6 V peak-to-peak voltage allowed precise positioning of the ZnO nanostructures at the edge of the metal electrodes. The physically formed p-Si (100) thin film/nanostructured n-ZnO heterojunction displayed multi-color emission from the ZnO near band edge as well as emission from defective states within the ZnO band gap.</P>
Jaehui Ahn,Geunwoo Ko,김지현,Michael A. Mastro,Jennifer Hite,Charles R. Eddy Jr. 한국물리학회 2010 Current Applied Physics Vol.10 No.2
This paper demonstrates the manipulation of neutral dielectric wires with high aspect ratio by a pulsed electric field. Dielectrophoretic (DEP) force and torque were employed to align the randomly positioned GaN nano- and micro-wires. A simulation of the DEP force alignment process confirmed the experimentally observed dependence on alignment yield to frequency and bias of the electric field. Current–voltage measurements of the GaN micro-wires, aligned by DEP force and torque to pre-patterned metal contacts,confirms that the direct manipulation of micro-sized wire with an electric field oscillated at a frequency of 10 kHz–5 MHz.
Characterization of AlGaN/GaN HEMT irradiated at 5 keV and 25 MeV proton energies
김홍렬,Jaehui Ahn,윤상필,Jae Sang Lee,김지현 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2
AlGaN/GaN high electron mobility transistors(HEMT) were irradiated at 5 keV and 25 MeV proton energies. Current-voltages were compared before and after proton irradiation. As expected from simulation results, 5 keV protons severely damaged the transistors’ performance compared to 25 MeV protons. Also, the effects of both low and higher fluencies were compared. Source-Drain currents were dramatically decreased under a higher fluency. Due to the extremely thin 2-Dimensional Electron Gas and the high displacement threshold energy, AlGaN/GaN HEMTs have great potential for applications in earth orbit.
김홍렬,Jaehui Ahn,김지현 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1
Gallium nitride on sapphire was characterized using AFM, SEM and micro-Raman spectroscopy after etching by a NOVA 200 FEI Focused Ion Beam (FIB). Various probe beam currents were used at a 30 kV acceleration voltage. The sidewall of the etched area was rougher and the roughness on the surface of the etched area increased when the probe beam current was increased. The intensity of the E2 2 phonon of micro-Raman spectroscopy decreased when the probe beam current was increased from 10pA, 100 pA, 1 nA to 20 nA. Therefore, it is very important to control the FIB probe current to maximize the etch rate and minimize the damage induced by accelerated Gallium ions.
Polarization and Space-Charge-Limited Current in III-Nitride Heterostructure Nanowires
Mastro, M. A.,Hong-Youl Kim,Jaehui Ahn,Simpkins, B.,Pehrsson, P.,Jihyun Kim,Hite, J. K.,Eddy, C. R. IEEE 2011 IEEE transactions on electron devices Vol.58 No.10
<P>An undoped AlGaN/GaN nanowire (NW) demonstrated p-type conductivity solely based on the formation of hole carriers in response to the negative polarization field at the (000-1) AlGaN/GaN facet. A transistor based on this NW displayed a low-voltage transition from ohmic to space-charge-limited conduction. A numerical simulation showed that a highly asymmetric strain exists across the triangular cross section, which creates a doublet peak in the piezoelectric-induced polarization sheet charge at the (000-1) facet. Additionally, there is a strong interplay between the charge at the (000-1) AlGaN/GaN interface with depletion from the three surfaces, as well as an interaction with the opposing polarization fields at two semipolar {- 110-1} facets. The charge distribution and resultant conduction regime is highly interdependent on the configuration of the multilayer structure, and it is not amenable to an analytical model.</P>
Group III-nitride radial heterojunction nanowire light emitters
Michael A. Mastro,Josh Caldwell,Mark Twigg,Blake Simpkins,Orest Glembocki,Ron T. Holm,Charles R. Eddy, Jr.,Fritz Kub,김홍렬,Jaehui Ahn,김지현 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
Heterojunction nanowires were fabricated via a vapor-liquid-solid growth mechanism in a metal organic chemical vapor deposition system. The structure consisted of a n-type GaN:Si core surrounding by a distinct p-type AlGaN:Mg shell. Transmission electron microscopy revealed that the nanowires were free of extended defects. Photoluminescence measured a strong UV emission peak. Additionally, sources of mid-gap transitions are linked to surface states on the nanowire surface.