• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.149-153
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• 2006

An attempting to produce a p-type diluted magnetic semiconductor (DMS) using $Ti_{1-x}Co_xO_{2-\delta}-based$ thin films was made by suitable control of the deposition parameters including deposition temperature, deposition pressure, and doping level using a pulsed laser deposition method. T$Ti_{0.97}Co_{0.03}O_{2-\delta}-based$ (TCO) films deposited at $500^{\circ}C$ at a pressure of $5\times10^{-6}$ Torr showed an anomalous Hall effect with p-type characteristics. On the other hand, films deposited at $700^{\circ}C$ at $5\times10^{-6}$ Torr showed n-type behaviors by a decreased solubility of cobalt. The charge carrier concentration in the p-type TCO films was approximately $7.9\times10^{22}/cm^3$ at 300 K and the anomalous Hall effect in the p-type TCO films was controlled by a side-jump scattering mechanism. The magnetoresistance (MR), measured at 5 K in p-type TCO films showed a positive behavior in an applied magnetic field and the MR ratio was approximately 3.5 %. The successful preparation of p-type DMS using the TCO films has the potential for use in magnetic tunneling junction devices.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.53-54
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• 2006

Arsenic doped p-type ZnO thin films have been realized on intrinsic (100) GaAs substrate by RF magnetron sputtering and thermal annealing treatment. p-Type ZnO exhibits the hole concentration of $9.684{\times}10^{19}cm^3$, resistivity of $2.54{\times}10^{-3}{\Omega}cm$, and mobility of $25.37\;cm^2/Vs$. Photoluminescence (PL) spectra of As doped p-type ZnO thin films reveal neutral acceptor bound exciton ($A^{0}X$) of 3.3437 eV and a transition between free electrons and acceptor levels (FA) of 3.2924 eV. Calculated acceptor binding energy ($E_A$) is about 0.1455 eV. Thermal activation and doping mechanism of this film have been suggested by using X-ray photoelectron spectroscopy (XPS). p-Type formation mechanism of As doped ZnO thin film is more related to the complex model, namely, $As_{Zn}-2V_{Zn}$, in which the As substitutes on the Zn site, rather than simple model, Aso, in which the As substitutes on the O site. ZnO-based p-n junction was fabricated by the deposition of an undoped n-type ZnO layer on an As doped p-type ZnO layer.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.303-308
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• 2011

The Gallium-doped ZnO(GZO) film deposited at a temperature of $200^{\circ}C$ and a pressure of 10 mtorr has an optical transmittance of 89.0% and a resistivity of $2.0\;m{\Omega}{\cdot}cm$ because of its high crystallinity. Effect of $Al_2O_3$ oxide buffer layers on the optical and electrical properties of sputtered ZnO films were intensively investigated for developing the electrodes of opto-electronic devices which demanded high optical transmittance and low resistivity. The use of $Al_2O_3$ buffer layer could increase optical transmittance of GZO film to 90.7% at a wavelength of 550 nm by controlling optical spectrum. Resistivity of deposited GZO films were much dependent on the deposition condition of $O_2/(Ar+O_2)$ flow rate ratio during the buffer layer deposition. It is considered that the $Al_2O_3$ buffer layer could increase the carrier concentration of the GZO films by doping effect of diffused Al atoms through the rough interface.

• Journal of IKEEE
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• v.17 no.2
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• pp.182-188
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• 2013

Using a ceramic target ZnO:In with In doping concentration of 2%, hetero-junctions of n-ZnO:In/p-Si and p-ZnO:(In, N)/n-Si were fabricated by depositing Indium doped n - type ZnO (ZnO:In or IZO) and Indium-nitrogen co-doped p - type ZnO (ZnO:(In, N)) films on wafers of p-Si (100) and n-Si (100) by DC magnetron sputtering, respectively. These films with the best electrical and optical properties were then obtained. The micro-structural, optical and electrical properties of the n-type and p-type semiconductor thinfilms were characterized by X-ray diffraction (XRD), RBS, UV-vis; four-point probe resistance and room-temperature Hall effect measurements, respectively. Typical rectifying behaviors of p-n junction were observed by the current-voltage (I-V) measurement. It shows fairly good rectifying behavior with the fact that the ideality factor and the saturation current of diode are n=11.5, Is=1.5108.10-7 (A) for n-ZnO:In/p-Si hetero-jucntion; n=10.14, Is=3.2689.10-5 (A) for p-ZnO:(In, N)/n-Si, respectively. These results demonstrated the formation of a diode between n-type thin film and p-Si, as well as between p-type thin film and n-Si..

• Journal of Radiation Protection and Research
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• v.28 no.2
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• pp.87-95
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• 2003

The fabrication process and the structure of PIN semiconductor detectors have been designed optimally by simulation for doping concentration and width of p+ layer, impurities re-contribution due to annealing and the current distribution due to guard ring at the sliced edges. The characteristics to radiation response has been also simulated in terms of Monte Carlo Method. The device has been fabricated on n type, $400\;{\Omega}cm$, orientation <100>, Floating-Zone silicon wafer using the simulation results. The leakage current density of $0.7nA/cm^2/100{\mu}m$ is achieved by this process. The good linearity of radiation response to Cs-137 was kept within the exposure ranges between 5 mR/h and 25 R/h. This proposed process could be applied for fabricating a PIN semiconductor detector for measuring individual dose.

• Carbon letters
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• v.27
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• pp.64-71
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• 2018

$TiO_2$-doped activated carbon fibers (ACFs) were successfully prepared as capacitive deionization (CDI) electrode materials by facile ultrasonication-assisted process. ACFs were treated with titanium isopropoxide (TTIP) and isopropyl alcohol solutions of different concentrations and then calcinated by ultrasonication without heat-treatment. The results show that a certain amount of anatase $TiO_2$ was present on the ACF surface. The specific capacitance of the $TiO_2$-doped ACF electrode was remarkably improved (by 93.8% at scan rate of $50mV\;s^{-1}$) over that of the untreated ACF electrode, despite decreases in the specific surface area and total pore volume upon $TiO_2$ doping. From the CDI experiments, the salt adsorption capacity and charge efficiency of the sample with TTIP percent concentration of 15% were found to considerably increase by 71.9 and 57.1%, respectively. These increases are attributed to the improved wettability of the electrode, which increases the number of surface active sites and facilitates salt ion diffusion in the ACF pores. Additionally, the Ti-OH groups of $TiO_2$ act as electrosorption sites, which increases the electrosorption capacity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.881-883
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• 2005

In case is below length 100nm of gate, various kinds problem can be happened with by threshold voltage change of device, occurrence of leakage current by tunneling because thickness of oxide by 1.5nm low scaling is done and doping concentration is increased. SiO$_2$ dielectric substance can not be used for gate insulator because is expected that tunneling current become 1A/cm$^2$ in 1.5nm thickness low. In this paper, devised double gate MOSFET(DGMOSFET) to decrease effect of leakage current by this tunneling. Therefore, could decrease effect of these leakage current in thickness 1nm low of SiO$_2$ dielectric substance. But, very big gate insulator of permittivity should be developed for develop device of nano scale.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.982-988
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• 2012

This paper has presented the relation of scaling theory and threshold voltage of double gate(DG) MOSFET. In the case of conventional MOSFET, current and switching frequency have been analyzed based on scaling theory. To observe the possibility of application of scaling theory for threshold voltage of DGMOSFET, the change of threshold voltage has been observed and analyzed according to scaling theory. The analytical potential distribution of Poisson equation has been used, and this model has been already verified. To solve Poisson equation, charge distribution such as Gaussian function has been used. As a result, it has been observed that threshold voltage is grealty changed according to scaling factor and change rate of threshold voltages is traced for scaling of doping concentration in channel. This paper has explained for the best modified scaling theory reflected the influence of two gates as using weighting factor when scaling theory has been applied for channel length and channel thickness.

• 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.