• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.5
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• pp.214-216
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• 2005

Photoreflectance (PR) has been measured to investigate the characterization of the $Al_{0.20}Ga_{0.80}As$/GaAs heterostructures. In the PR spectrum, the 'C' peak is confirmed as the carbon defect with residual impurity originating from the growth process. After annealing, binding energy is relatively weak with As evaporation being done to increase Ga. Also obtained is the electric field value according to annealing temperature ($300{\sim}800^{\circ}C$).

• Journal of Preventive Medicine and Public Health
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• v.32 no.4
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• pp.467-472
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• 1999

Objectives: This study was conducted to evaluate the cytotoxicity of gallium arsenide(GaAs), indium phosphide(InP) and indium arsenide(InAs) all of which are used a$ the semiconductor eletments in semiconductor industry. Methods: Cytotoxicity id the alveolar macrophage was evaluated by the measurement of in vitro magnetometry, LDH release assay and histological examination. Results: The relaxation curves by the in vitro magnetometry showed that GaAs has the cytotoxicity for the alveolar macrophage which is more significant in the higher dosages, while this cytotoxicity is not appeared in the groups added with InP or InAs or PBS. In the decay constant for two minutes after magnetization, GaAs-added groups showed a significant decrease with increasing doses, but both InP- and InAs-added groups did not show any significance. The LDH release assay showed a dose-dependent increasing tendency in the GaAs-, InP- and InAs-added groups. In terms of cellular morphological changes, GaAs-added groups revealed such severe cellular damages as prominent destructions in cell membranes and their morphological changes of nucleus, while InP- and InAs-added groups remained intact in intracellular structures, except for cytoplasmic degenerations. Conclusions: It is suggested that GaAs is more influential to cytotoxicity of alveolar macrophages than InP and InAs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.19-24
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• 2004

In this paper, we have demonstrated the fabrication of a 70 nm foot print of the T-gate by using a positive resist ZEP520/P(MMA-MAA)/PMMA trilayer by double exposure method without a thin dielectric supporting layer on the substrate. The device performance was characterized by DC and RF measurement. The fabricated 70 nm InGaAs/InAlAs MHEMTS with 70 ${\mu}{\textrm}{m}$ unit gate width and 2 fingers showed good DC and RF characteristics of Idss, max =228.6 mA/mm, gm =645 mS/mm, and fT =255 GHz, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.915-922
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• 1999

The field dependent characteristics of electron transport with GaAs impact ionization have been analyzed, using GaAa full band E-k relationship. The E-k relationship is derived from empirical pseudopotential method, using Fermi's golden rule and local form factor, and Brillouin zone is divided into tetrahedrons for calculating impact ionization rate, and tetrahedron method, in which integrates each tetrahedrons, is used. Monte Carlo simulation is used for analyzing anisotropy of impact ionization. A result of transient analysis for impact ionization has presented that anisotropy of impact ionization only arises during transient state and impact ionization is isotropic under steady state. Anisotropic characteristics of impact ionization for GaAs, which is presented in this paper, can be used in carrying out a transient analysis for GaAs devices.

• Journal of Sensor Science and Technology
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• v.10 no.5
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• pp.304-313
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• 2001

In this research, we investigate wet-etching properties of GaAs in $NH_4OH-H_2O_2-H_2O$, and develop the fabrication method of GaAs microstructures with rectangular cross section using (001) GaAs substrate. For obtaining wet-etching properties with respect to crystallographic orientation, the etch rates and cross-section etch profiles of (001) GaAs with 16 different compositions and the undercut rates with 5 different compositions are measured using $NH_4OH-H_2O_2-H_2O$ mixed solutions. From these experimental data, a new GaAs micromachining method in bulk (001) GaAs is proposed, and used to fabricate a released microbridges with a rectangular cross section. The developed GaAs micromachining method can be very useful for low-loss, highly-tunable capacitors for RF components and for integration with GaAs optical components.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.840-843
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• 2001

In this study, temperature dependency of current gain for AlGaAs/GaAs/GaAs HBT is analytically proposed over the temperature range between 300K and 600K. Energy bandgap, effective mass, intrinsic carrier concentration are considered as temperature dependent parameters. Collector current which is numerically calculated is then analytically expressed to enhance the speed of calculation for current gain. From the results, current gain decreases as the temperature increases. These results will be used to expect the unity current gain frequency f$_{T}$ in conjunction with emitter-base and collector- base capacitances.s.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.69-74
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• 1995

GaAs tilt grain boundaries were propared by growing GaAs epilayers on Ge bicrystals by an organometallic vapor phase epitaxy (OMVPE) method ∑ =9 tilt grain boundaries were produced when two different first-order twin boundaries interacted with one another in GaAs epilayers. Structural investigations were performed for the coherent and second-order twin boundaries of GaAs by high-resolution transmission electron microscopy (HRTEM). Polarities of cross-boundary bondings were determined from the high-order Laue zone (HOLZ) lines in the (200) convergent beam disks : these were recorded from the two grains on either side of the boundaries, respectively, at particular diffraction conditions.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.200-201
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• 1998

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.98-98
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• 1996

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.438-440
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• 2008

Effects of Ga contents of CIGS absorber layer on the performance of thin films solar cells were investigated. As Ga content increased, the grain size of CIGS films decreased presumably because Ga diffusion during 2nd stage of co-evaporation process is more difficult than In diffusion. Performances of corresponding solar cell show systematic dependence on Ga content in which open circuit voltage increases and short circuit current and fill factor decrease as Ga contents increases. At a optimal condition of Ga/(In+Ga)=0.27, the solar cell shows a conversion efficiency of 15.6% with $V_{OC}$ of 0.625 V, $J_{SC}$ of 35.03 mA/$cm^2$ and FF of 71.3%.