• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.968-972
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• 2008

Ni/Ti/Al multilayer system ('/'denotes the deposition sequence) was tested for low-resistance ohmic contact formation to Al-implanted p-type 4H-SiC. Ni 30 nm / Ti 50 nm / Al 300 nm layers were sequentially deposited by e-beam evaporation on the 4H-SiC samples which were implanted with Al (norminal doping concentration = $4\times10^{19}cm^{-3}$) and then annealed at $1700^{\circ}C$ for dopant activation. Rapid thermal anneal (RTA) temperature for ohmic contact formation was varied in the range of $840\sim930^{\circ}C$. Specific contact resistances were extracted from the measured current vs. voltage (I-V) data of linear- and circular transfer length method (TLM) patterns. In constrast to Ni contact, Ni/Ti/Al contact shows perfectly linear I-V characteristics, and possesses much lower contact resistance of about $2\sim3\times10^{-4}\Omega{\cdot}cm^2$ even after low-temperature RTA at $840^{\circ}C$, which is about 2 orders of magnitude smaller than that of Ni contact. Therefore, it was shown that RTA temperature for ohmic contact formation can be lowered to at least $840^{\circ}C$ without significant compromise of contact resistance. X-ray diffraction (XRD) analysis indicated the existence of intermetallic compounds of Ni and Al as well as $NiSi_{1-x}$, but characteristic peaks of $Ti_{3}SiC_2$, a probable narrow-gap interfacial alloy responsible for low-resistance Ti/Al ohmic contact formation, were not detected. Therefore, Al in-diffusion into SiC surface region is considered to be the dominant mechanism of improvement in conduction behavior of Ni/Ti/Al contact.

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.196-200
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• 2016

We have developed new electrostatic discharge (ESD) protection devices with, bidirectional flip chip transient voltage suppression. The devices differ in their epitaxial (epi) layers, which were grown by reduced pressure chemical vapor deposition (RPCVD). Their ESD properties were characterized using current-voltage (I-V), capacitance-voltage (C-V) measurement, and ESD analysis, including IEC61000-4-2, surge, and transmission line pulse (TLP) methods. Two BD-FCTVS diodes consisting of either a thick (12 μm) or thin (6 μm), n-Si epi layer showed the same reverse voltage of 8 V, very small reverse current level, and symmetric I-V and C-V curves. The damage found near the corner of the metal pads indicates that the size and shape of the radius governs their failure modes. The BD-FCTVS device made with a thin n- epi layer showed better performance than that made with a thick one in terms of enhancement of the features of ESD robustness, reliability, and protection capability. Therefore, this works confirms that the optimization of device parameters in conjunction with the doping concentration and thickness of epi layers be used to achieve high performance ESD properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.6
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• pp.491-496
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• 2011

Al-doped ZnO film on glass substrate is deposited by ALD in low temperature, using 4-step process (DEZ-$H_2O$-TMA-$H_2O$). To find out the optimal film condition for TCO material, we fabricate Al-doped ZnO films by increasing Al doping concentration at $100^{\circ}C$, so that the Al-doped film of 5 at% shows the lowest resistivity ($1.057{\times}10^{-2}{\Omega}{\cdot}cm$) and the largest grain size (38.047 nm). Afterwards, the electrical and physical characteristics in Al-doped films of 5 at% are also compared in accordance with increasing deposition temperature. All the films show the optical transmittance over 80% and the film deposited at $250^{\circ}C$ demonstrates the superior resistivity ($1.237{\times}10^{-4}{\Omega}{\cdot}cm$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.662-667
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• 2014

B-doped Si nanoparticles were synthesized by using inductive coupled plasma and specially designed double tube reactor, and their microstructures were investigated. 0~10 sccm of $B_2H_6$ gas was injected during the synthesis of Si nanoparticles from $SiH_4$ gas. Highly crystalline Si nanoparticles were synthesized, and their crystallinity did not change with increase of $B_2H_6$ flow rates. From SEM measurement, their particle sizes were approximately 30 nm regardless of $B_2H_6$ flow rates. From SIMS analysis, almost saturation of B in Si nanoparticles was detected only when 1 sccm of $B_2H_6$ was injected. When $B_2H_6$ flow rate exceeded 5 sccm, higher concentration of B than solubility limit was detected even if any secondary phase was not detected in XRD or HR-TEM results. Due to their high electronic conductivity, those heavily B-doped Si nanoparticles can be a potential candidate for an active material in Li-ion battery anode.

• Korean Journal of Materials Research
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• v.2 no.5
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• pp.360-365
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• 1992

Ga-doped polycrystalline ZnO films on glass substrates were prepared by sputtering the targets, which had been prepared by sintering discs consisting of ZnO powder and various amounts of G$a_2O_3$, to investigate the effects of gallium doping and sputtering conditions on electrical properties. Optimizing the RF power density, argon gas pressure and gallium content, transparent Ga-doped ZnO films with resistivity less than 1$0^{-3}$ohm-cm are obtained. Electron concentration of undoped and Ga-doped ZnO films are order of $10^{18}$, $10^{21}$/c$m^2$respectively. After heat treatment in air and $N_2atmosphere, $ the resistivity of Ga-doped ZnO films increases by about two orders of magnitude. The optical transmission is above 80% in the visible range and the optical band widens as the Ga content increases.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.629-632
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• 2006

Electrical characteristics of Pt/Ti/Pt/Au and Pd/Zn/Pd/Au contacts to p-type InGaAs grown on an InP substrate have been characterized as a function of the doping concentration and the annealing temperature. The Pt/Ti/Pt/Au contacts produced the specific contact resistance as low as $2.3{\times}10^{-6}{\Omega}{\cdot}cm^2$, when heat-treated at an annealing temperature of $400^{\circ}C$. Comparison of the Pt/Ti/Pt/Au and Ti/Pt/Au contacts showed that the first Pt layer plays an important role in reducing the contact resistivity probably by lowering energy barrier at the metal-semiconductor interface. For the Pd/Zn/Pd/Au contacts, the contact resistivity remained virtually unchanged with increasing annealing temperature. The specific contact resistivity as low as $4.7{\times}10^{-6}{\Omega}{\cdot}cm^2$ was obtained. The results indicate that the Pt/Ti/Pt/Au and Pd/Zn/Pd/Au schemes could be potentially important for the fabrication of InP-based optoelectronic devices, such as photodetector and optical modulator.

• Korean Journal of Materials Research
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• v.18 no.2
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• pp.84-91
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• 2008

The effects of the deposition and annealing temperature on the structural, electrical and optical properties of Ag doped ZnO (ZnO : Ag) thin films were investigated. All of the films were deposited with a 2wt% $Ag_2O-doped$ ZnO target using an e-beam evaporator. The substrate temperature varied from room temperature (RT) to $250^{\circ}C$. An undoped ZnO thin film was also fabricated at $150^{\circ}C$ as a reference. The as-grown films were annealed in temperatures ranging from 350 to $650^{\circ}C$ for 5 h in air. The Ag content in the film decreased as the deposition and the post-annealing temperature increased due to the evaporation of the Ag in the film. During the annealing process, grain growth occurred, as confirmed from XRD and SEM results. The as-grown film deposited at RT showed n-type conduction; however, the films deposited at higher temperatures showed p-type conduction. The films fabricated at $150^{\circ}C$ revealed the highest hole concentration of $3.98{\times}1019\;cm^{-3}$ and a resistivity of $0.347\;{\Omega}{\cdot}cm$. The RT PL spectra of the as-grown ZnO : Ag films exhibited very weak emission intensity compared to undoped ZnO; moreover, the emission intensities became stronger as the annealing temperature increased with two main emission bands of near band-edge UV and defect-related green luminescence exhibited. The film deposited at $150^{\circ}C$ and annealed at $350^{\circ}C$ exhibited the lowest value of $I_{vis}/I_{uv}$ of 0.05.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.4
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• pp.754-759
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• 2007

Field emission displays (FED) are currently being explored as a potential flat panel display technology. Specifically, the optimization pf efficient bin emitting phosphors in the $Y_2O_3-Nb_2O_5$ system and influence of particle size of phosphors on the luminescent properties was studied. Under 254 nm excitation, Bi activated $YNbO_4$ phosphors showed a strong and relatively narrow blue omission band, peaking at about 420-450 nm. Especially 0.4 wt% Bi doped yttrium phosphors showed the maximum emission intensity which is almost three times as much as that of $Y_2SiO_5:Ce$ phosphors. Finally, Ce doped $Y_2SiO_5$ phosphors exhibited strong and broad blue emission band, centered at 390-420 nm and maximum emission intensity at the doping concentration of 0.02-0.03 mol.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.847-854
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• 2012

Al-doped ZnO (AZO) thin films were grown on quartz substrates by the sol-gel method. The effects of the Al mole fraction on the structural and optical properties of the AZO thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-VIS spectroscopy. The particle size of the AZO thin films decreased with an increase in Al concentrations. The optical parameters, the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity, were studied in order to investigate the effects of Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at an infinite wavelength of the AZO thin films were affected by the Al incorporation. The optical conductivity of the AZO thin films also increased with increasing photon energy.

• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1058-1064
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• 1994

Mn/In$_2O_3$ systems with a variety of Mn mol${\%}$ were prepared to investigate the effect of Mn-addition on the catalytic activity of Mn/In$_2O_3$ in the oxidative coupling of methane. The oxidative coupling of methane was examined on pure In$_2O_3$ and Mn/In$_2O_3$ catalysts by cofeeding gaseous methane and oxygen under atmospheric pressure between 650 and 830 $^{\circ}C$. Although pure In$_2O_3$ showed no C$_2$ selectivity, both the C$_2$ yield and the C$_2$ selectivity were increased by Mn-doping. The 5.1 mol${\%}$ Mn-doped In$_2O_3$ catalyst showed the best C$_2$ yield of 2.6${\%}$ with a selectivity of 19.1${\%}$. The electrical conductivities of pure and Mn-doped In$_2O_3$ systems were measured in the temperature range of 25 to 100 $^{\circ}C$ at PO$_2$'S of 1 ${\times}$ 10$^{-7}$ to 1 ${\times}$ 10 $^{-1}$ atm. The electrical conductivities were decreased with increasing Mn mol${\%}$ and PO$_2$, indicating the specimens to be n-type semiconductors. Electrons serve as the carriers and manganese can act as an electron acceptor in the specimens. Manganese ions doped in In$_2O_3$ inhibit the ionization of neutral interstitial indium or the transfer of lattice indium to interstitial sites and increase the formation of oxygen vacancy, giving rise to the increase of the concentration of active oxygen ion on the surface. It is suggested that the active oxygen species adsorbed on oxygen vacancies are responsible for the activation of methane.