• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.66-69
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• 2003

Various semiconductor nanowires such as GaN, GaP, InP, Si$_3$N$_4$, SiO$_2$/Si, and SiC were coated conformally with aluminum oxide (Al$_2$O$_3$) layers by atomic layer deposition (ALD) using trimethylaluminum (TMA) and distilled water ($H_2O$) at a temperature of 20$0^{\circ}C$. Transmission electron microscopy (TEM) revealed that A1203 cylindrical shells conformally coat the semiconductor nanowires. This study suggests that the ALD of $Al_2$O$_3$ on nanowires is a promising method for preparing cylindrical dielectric shells for coaxially gated nanowire field-effect transistors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.128-134
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• 1996

In this study, the thermal and optical properties of multicomponent glass optical fiber by adding heavy metal oxide Ga$_2$O$_3$were investigated. The fiber samples were made by rod in tube method. The optical loss of fiber was measured in 0.3~1.8${\mu}{\textrm}{m}$ wavelength region. As Ga$_2$O$_3$increased up to 20wt%, the transition and softening temperature of bulk glass were increased from 495$^{\circ}C$ to 579$^{\circ}C$ and from 548$^{\circ}C$ to 641$^{\circ}C$respectively. Whereas the thermal expansion coefficient was decreased from 102 to 79.1$\times$10$^{-7}$ $^{\circ}C$. The refractive index was increased from 1.621 to 1.665, and IR cut-off wavelength was enlarged from 4.64${\mu}{\textrm}{m}$ to 6.1${\mu}{\textrm}{m}$. The optical loss of fiber was decreased and more remarkably decreased in 1.146${\mu}{\textrm}{m}$~1.8${\mu}{\textrm}{m}$ wavelength region.

• Journal of Magnetics
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• v.19 no.2
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• pp.126-129
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• 2014

We report the crystallographic and magnetic properties of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a M$\ddot{o}$ssbauer spectroscopy. In particular, $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was studied by M$\ddot{o}$ssbauer analysis for evidence of spin reorientation. The chalcogenide material $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was fabricated by a direct reaction method. XRD analysis confirmed that $Ni_{0.3}Fe_{0.7}Ga_2S_4$ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The M$\ddot{o}$ssbauer spectra of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, $E_Q$ has anomalous two-points of temperature dependence of $E_Q$ curve as freezing temperature, $T_f=11K$, and N$\acute{e}$el temperature, $T_N=26K$. This suggests that there appears to be a slowly-fluctuating "spin gel" state between $T_f$ and $T_N$, caused by non-paramagnetic spin state below $T_N$. This comes from charge re-distribution due to spin-orientation above $T_f$, and $T_N$, due to the changing $E_Q$ at various temperatures. Isomer shift value ($0.7mm/s{\leq}{\delta}{\leq}0.9mm/s$) shows that the charge states are ferrous ($Fe^{2+}$), for all temperature range. The Debye temperature for the octahedral site was found to be ${\Theta}_D=260K$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.234-238
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• 2005

Effects of plasma composition, ion flux and ion energy on the etch rate, surface morphology and near surface stoichiometry of a single crystalline $La_3Ga_5SiO_{14}$ wafer have been examined in $Cl_2/Ar$ inductively coupled plasma (ICP) discharges. Maximum etch rate ${\sim}1600{\AA}/min$ was achieved either at relatively high source power $({\sim}1000W)$ or high $Cl_2$ content conditions in $Cl_2/Ar$ discharges. The etched surfaces showed similar or better RMS roughness values than those of the unetched control sample and the near surface stoichiometry was found not to be affected by ICP etching.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.860-864
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• 1998

We investigated the photoluminescence and the crystalline properties with Ga doping concentrations (0-12 mol%) in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}\textrm{SiO}_{4}$ green phosphors prepared by the solid state reaction. The photoluminescence was improved by a doping of Ga element in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$ phosphors which showed the highest emission intensity and good color purity in the doping concentration of x=0.08. The emission intensity of $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$(x= 0.08) phosphors was increased to 7 times with increasing the sintering temperatures from $1100^{\circ}C$ to $1400^{\circ}C$, showing the improved crystalline quality. The decay time was not affected by Ga doping concentrations with constant values around 24ms. It was found from SEM and PSA analyses that the phosphors were composed of a large number of small grains around 1-3$10\mu\textrm{m}$ with a small amounts of agglomerated particles above $10\mu\textrm{m}$.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.108-115
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• 2018

The increasing demands for three-dimensional (3D) electronic and optoelectronic devices have triggered interest in epitaxial growth of 3D semiconductor materials. However, most of the epitaxially-grown nano- and micro-structures available so far are limited to certain forms of crystal arrays, and the level of control is still very low. In this review, we describe our latest progress in 3D epitaxy of oxide and nitride semiconductor crystals. This paper covers issues ranging from (i) low-temperature solution-phase synthesis of a well-regulated array of ZnO single crystals to (ii) systematic control of the axial and lateral growth rate correlated to the diameter and interspacing of nanocrystals, as well as the concentration of additional ion additives. In addition, the critical aspects in the heteroepitaxial growth of GaN and InGaN multilayers on these ZnO nanocrystal templates are discussed to address its application to a 3D light emitting diode array.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.17-21
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• 2012

Ga-doped ZnO (GZO) thin films for application as transparent conducting oxide film were deposited on the glass substrate by using rf-magnetron sputtering system. The effects of working pressure on electrical and optical characteristics of GZO films were investigated. Regardless of the working pressure, all films were oriented along with the c-axis, perpendicular to the substrate. The electrical resistivity was about $8.68{\times}10^{-3}{\Omega}{\cdot}cm\sim2.18{\times}10^{-3}{\Omega}{\cdot}cm$ and the average transmittance of all films including substrates was over 90% in the visible range. The good transparents and conducting properties were obtained due to controle the working pressure. The obtained results have acceptable for application as transparent conductive electrodes in LCDs and solar cells.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.364-370
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• 1995

The catalytic oxidations of several olefins in $CH_2Cl_2$ have been investigated using non-redox metalloporphyrin (M=Ga(III), In(III), Tl(III)) complexes as catalyst and sodium hypochlorite as terminal oxidant. Porphyrins were $(p-CH_3O)TPP,\;(p-CH_3)TPP,\;TPP,\;(p-F)TPP,\;(p-Cl)TPP\;and\;(F_20)TPP$ (TPP=tetraphenylporphyrin), and olefins were $(p-CH_3O)-,\;(p-CH_3)-,\;(p-H)-,\;(p-F)-,\;(p-Cl)-\;and\;(p-Br)styrene$styrene and cyclopentene and cyclohexene. The substrate conversion yield was discussed according to the substituent effects of metalloporphyrin and substrate, and the radius effect of non-redox metal ion. The conversion yield of substrate by changing the substituent of TPP increased in the order of $p-CH_3O$ < $p-CH_3$ < H < p-F < p-Cl, which was consistent with the sequence of $4{\sigma}$ values of TPP. But the substituent effect of substrate on the conversion yield decreased with increasing the ${\sigma}^+$ values on substrates in the order of p-CH3O > p-CH3 > H > p-Cl > p-Br. For the oxidation of several olefins, the complexes of In(III)- and Tl(III)-porphyrins turned out to be more active catalysts than Ga(III)-porphyrin.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.335-340
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• 2001

$Ga_2O_3$(1 wt%)-doped ZnO(GZO) thin films were grown on ${\alpha}-Al_2O_3$ (0001) by rf magnetron sputtering at $510^{\circ}C$, whose crystal structure was polycrystalline. As-grown GZO thin film shows poor electrical properties and photoluminescence (PL) spectra. To improve these properties, GZO thin films were annealed at 800-$900^{\circ}C$ in $N_2$atmosphere for 3 min. After the rapid thermal annealing(RTA), deep defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resisitivity of $2.6\times10^{-4}\Omega$/cm with $3.9\times10^{20}/\textrm{cm}^3$ carrier concentration and exceptionally high mobility of 60 $\textrm{cm}^2$/V.s. These improved physical properties are explained in terms of translation of doped-Ga atoms from interstitial to substitutional site.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.266-269
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• 2020

In this study, we investigated the effect of a sulfur passivation (S-passivation) process step on the electrical properties of surface-channel In_0.7Ga_0.3As quantum-well (QW) metal-oxide-semiconductor field-effect transistors (MOSFETs) with S/D regrowth contacts. We fabricated long-channel In_0.7Ga_0.3As QW MOSFETs with and without (NH₄)₂S treatment and then deposited 1/4 nm of Al₂O₃/HfO₂ through atomic layer deposition. The devices with S-passivation exhibited lower values of subthreshold swing (74 mV/decade) and drain-induced barrier lowering (19 mV/V) than the devices without S-passivation. A conductance method was applied, and a low value of interface trap density D_it (2.83×10¹² cm^-2eV^-1) was obtained for the devices with S-passivation. Based on these results, interface traps between InGaAs and high-κ are other defect sources that need to be considered in future studies to improve III-V microsensor sensing platforms.