• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.310-310
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• 2012

ZnO thin films were grown on porous silicon (PS) by plasma-assisted molecular beam epitaxy (PA-MBE). The optical properties of the ZnO thin films grown on PS were studied using room-temperature, low-temperature, and temperature-dependent photoluminescence (PL). The full width at half maximum (FWHM) of the near-band-edge emission (NBE) from the ZnO thin films was 98 meV, which was much smaller than that of ZnO thin films grown on a Si substrate. This value was even smaller than that of ZnO thin films grown on a sapphire substrate. The Huang-Rhys factor S associated with the free exciton (FX) emission from the ZnO thin films was found to be 0.124. The Eg(0) value obtained from the fitting was 3.37 eV, with ${\alpha}=3.3{\times}10^{-2}eV/K$ and ${\beta}=8.6{\times}10^3K$. The low- and high-temperature activation energies were 9 and 28 meV, respectively. The exciton radiative lifetime of the ZnO thin films showed a non-linear behavior, which was established using a quadratic equation.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.387-390
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• 2002

A new approach of using double buffer layers of AlN and GaN for growth of GaN films on Si has been undertaken via molecular beam epitaxy using ammonia. The first buffers layer of AlN was grown using $N_2$plasma and the second of GaN was grown using ammonia. The surface roughness of the grown films was investigated by atomic force microscope and was compared with the normally grown films on sapphire. Double crystal x-ray rocking curve and low temperature photoluminescence techniques were employed for structural and optical properties examination. Donor bound exciton peak at 3.481 eV with full width half maximum of 41 meV was observed at 13K.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.251-256
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• 2003

Indium aluminum arsenide(InAlAs) was grown by molecular beam epitaxy on (001) indium phosphide (InP) substrate and the effects of growth temperature on the properties of epitaxial layers were studied. In the temperature range of 370-$400 ^{\circ}C$, we observed that the surface morphology, optical quality and structural quality of InAlAs epilayers were improved as growth temperature increased. However, the InAlAs epilavers grown at $430 ^{\circ}C$ have the bad surface morphology and show the same trends as structural and epical quality. As a result of these measurements, it is suggested that the InAlAs epilayers of very good properties can be grown at $400 ^{\circ}C$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.349-350
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• 2012

Porous silicon (PS) was prepared by electrochemical anodization. Ultra-thin zinc oxide (ZnO) capping layers were deposited on the PS by plasma-assisted molecular beam epitaxy (PA-MBE). The effects of the ZnO capping layers on the properties of the as-prepared PS were investigated using scanning electron microscopy (SEM) and photoluminescence (PL). The as-prepared PS has circular pores over the entire surface. Its structure is similar to a sponge where the quantum confinement effect (QCE) plays a fundamental role. It was found that the dominant red emission of the porous silicon was tuned to white light emission by simple deposition of the ultra-thin ZnO capping layers. Specifically, the intensity of white light emission was observed to be enhanced by increasing the growth time from 1 to 3 min.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.515-519
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• 1999

We have investigated the photoreflectance characteristics for In\ulcornerGaAs/GaAs heterojunction structure grown by molecular beam epitaxy (MBE). The E\ulcorner bandgap energy of In\ulcornerGa\ulcornerAs at room temperature was observed at about 1.3 eV. From this result, the indium composition x value was calculated. The shoulder peaks were observed higher than E\ulcorner peaks, and peak positions were shifted toward 12 meV to 70 meV higher energy with increasing doping concentrations. The shoulder peaks can be observed by In segregation and re-evaporation. However, we think that indium re-evaporation cause th shift of shoulder peaks after epilayer growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.175-177
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• 2002

Electrical characteristics of the Si-O superlattice diode as a function of annealing conditions have been studied. The nanocrystalline silicon/adsorbed oxygen superlattice formed by molecular beam epitaxy (MBE) system. Consequently, the experimental results of superlattice diode with multilayer Si-O structure showed the stable and good insulating behavior with high breakdown voltage. This is very useful promise for Si-based optoelectronic and quantum device as well as for the replacement of silicon-on-insulator (SOI) in ultra high speed and lower power CMOS devices in the future, and it can be readily integrated with silicon ULSI processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.202-205
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• 2002

The photoluminescence (PL) characteristics of the silicon-oxygen(Si-O) superlattice formed by molecular beam epitaxy (MBE) were studied. To confirm the presence of the nanocrystalline Si structure, Raman scattering measurement was performed. The blue shift was observed in the PL peak of the oxygen-annealed sample, compared to the hydrogen-annealed sample, which is due to a contribution of smaller crystallites. Our results determine the right direction for the fabrication of silicon-based optoelectronic and quantum devices as well as for the replacement of silicon-on-insulator (SOI) in high-speed and low-power silicon MOSFET devices in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.551-556
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• 2000

We have investigated the effect of surface In composition with Si cell temperature on the In$_{0.1}$/Ga$_{0.9}$/As epilayers grown on GaAs substrates. The epilayers were grown by molecular beam epitaxy(MBE) method and were characterized by the pthotoreflectance(PR) measurements. The E$_{o}$ bandgap energies of In$_{0.1}$/Ga$_{0.9}$/As epilayers were observed at around 1.28 eV at room temperature, and the additional shoulder peaks appeared at the higher energies than E$_{o}$ with increase of Si doping concentrations. The intensity of the additional shoulder peak was decreased with lowering the measurement temperature and the peak disappeared with the increase of surface etching time. This results hows that In composition at surface of InGaAs epilayer is decreased with the increase of the doping cell temperature. We consider that the reason of the decrease of In composition at the surface should be due to In re-evaporation from the surface by radiation heat of Si doping cell.ell.ell.ell.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.167-168
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• 2006

High quality 3D-heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources ($As_2$, $As_4$) were varied to calibrate the selective area growth conditions. Scanning micro-photoluminescence ($\mu$-PL) measurements and following analysis revealed that the gradually (adiabatically) coupled 2DEG-1D-1DEG field effect transistor (FET) system was realized. This 3D-heterostructure is very promising for the realization of the meso-scopic electronic devices and circuits since it makes it possible to form direct ohmic contact to the (quasi) 1DEG.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.371-376
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• 2010

The GaAs epitaxial layers were grown on Si(100) substrates by molecular beam epitaxy (MBE) using the two-step method. The Si(100) substrates were cleaned with three different surface cleaning methods of vacuum heating, As-beam exposure, and Ga-beam deposition at the substrate temperature of $800^{\circ}C$ in the MBE growth chamber. Growth temperature and thickness of the GaAs epitaxial layer were $800^{\circ}C$ and $1{\mu}m$, respectively. The surface structure and properties were investigated by reflection high-energy electron diffraction (RHEED), AFM (Atomic force microscope), DXRD (Double crystal x-ray diffraction), PL (Photoluminescence), and PR (Photoreflectance). From RHEED, the surface structure of GaAs epitaxial layer grown on Si(100) substrate with Ga-beam deposition is ($2{\times}4$). The GaAs epitaxial layer grown on Si(100) substrate with Ga-beam deposition has a high quality.