• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.297-297
• /
• 2010

Transparent conductive Oxide (TCO) is an essential material in the various optoelectronic applications as a transparent electrode, such as solar cells, flat panel displays and organic light emitting diodes. Currently, Indium tin oxide (ITO) is commonly used in industry due to its low electrical resistivity, high transmittance and high adhesion to substrate. However, ITO is expensive and should be prepared at high temperature, which makes it hard to use ITO in flexible devices. In this regard, Ga-doped ZnO is expected as an ideal candidate for replacing ITO.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.37 no.1
• /
• pp.27-34
• /
• 2000

In this paper, carrier transport mechanism and modulation response for SCH(Separate Confinement Heterostructure) SQW(Single Quantum Well) laser diodes were studied. In order to explain carrier transport mechanism, both carrier density and current density were calculated. The recombination current density in the quantum well as a function of the SCH length was also calculated. For the modulation response, linearizing the rate equation, we calculated the bandwidth, relaxation oscillation frequency, damping factor, and the K-factor.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1359-1360
• /
• 2006

lTO(Indium-Tin-Oxide) was used as anode material for OLED. Characteristics of ITO have great effect on efficiency of OLEDS(Organic light emitting diodes). ITO surface was treated by Nd:YAG laser in order to improve its chemical properties, wettability, adhesive property and to remove the surface contaminants while maintaining its original function. In this study, main purpose was to improve the efficiency of OLEDs by the ITO surface treatment: ITO surface was treated using a Nd:YAG(${\lambda}=266nm$, pulse) with a fixed power of 0.06[w] and various stage scanning velocities. Surface morphology of the ITO was investigated by AFM. Test OLEDs with surface treated ITO were fabricated by deposition of TPD (HTL), Ald3 (ETL/TML) and Al (cathode) thin films. Device performance of the OLEDs such as V-I-L was investigated using Source Measurement Unit (SMU: Keithly. Model 2400) and Luminance Measurement (TOPCON. BM-8).

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1381-1387
• /
• 2018

One dimensional (1D) grating has been fabricated (using focused ion beam) on 50 nm gold (Au) film deposited on higher refractive index Gallium phosphate (GaP) substrate. The sub-wavelength periodic metal nano structuring enable to couple photon to couple with the surface plasmons (SPs) excited by them. These grating devices provide the efficient control on the SPs which propagate on the interface of noble metal and dielectric whose frequency is dependent on the bulk electron plasma frequency of the metal. For a fixed periodicity (${\Lambda}=700 nm$) and slit width (w = 100 nm) in the grating device, the efficiency of SPP excitation is about 40% compared to the transmission in the near-field. Efficient coupling of SPs with photon in dielectric provide field localisation on sub-wavelength scale which is needed in Heat Assisted Magnetic recording (HAMR) systems. The GaP is also used to emulate Vertical Cavity Surface emitting laser (VCSEL) in order to provide cheaper alternative of light source being used in HAMR technology. In order to understand the underlying physics, far-and near-field results has been compared with the modelling results which are obtained using COMSOL RF module. Apart from this, grating devices of smaller periodicity (${\Lambda}=280nm$) and slit width (w = 22 nm) has been fabricated on GaP substrate which is photoluminescence material to observe amplified spontaneous emission of the SPs at wavelength of 805 nm when the grating device was excited with 532 nm laser light. This observation is unique and can have direct application in light emitting diodes (LEDs).

• Korean Journal of Materials Research
• /
• v.33 no.6
• /
• pp.229-235
• /
• 2023

An all-perovskite oxide heterostructure composed of SrSnO₃/Nb-doped SrTiO₃ was fabricated using the pulsed laser deposition method. In-plane and out-of-plane structural characterization of the fabricated films were analyzed by x-ray diffraction with θ-2θ scans and φ scans. X-ray photoelectron spectroscopy measurement was performed to check the film's composition. The electrical transport characteristic of the heterostructure was determined by applying a pulsed dc bias across the interface. Unusual transport properties of the interface between the SrSnO₃ and Nb-doped SrTiO₃ were investigated at temperatures from 100 to 300 K. A diodelike rectifying behavior was observed in the temperature-dependent current-voltage (IV) measurements. The forward current showed the typical IV characteristics of p-n junctions or Schottky diodes, and were perfectly fitted using the thermionic emission model. Two regions with different transport mechanism were detected, and the boundary curve was expressed by ln I = -1.28V - 13. Under reverse bias, however, the temperature- dependent IV curves revealed an unusual increase in the reverse-bias current with decreasing temperature, indicating tunneling effects at the interface. The Poole-Frenkel emission was used to explain this electrical transport mechanism under the reverse voltages.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.2
• /
• pp.81-89
• /
• 1999

Among various wavelength conversion technologies, that using the cross-gain modulation in laser diode makes it possible to deal with the high speed signal quite simply and efficiently. In this paper, presented was the applicability of an improved time-domain large-signal dynamic model as a CAD tool to analyzed the characteristics of SSGDBR(Superstructure Grating Distributed Bragg Reflector) laser diodes used for wavelength converters. Using this model, it was shown that this kind of wavelength converter can provide the widely tunable wavelength conversion of the high speed data above 10 Gbps. We also investigated the effect of input optical power and the bias current on the characteristics of the device such as extinction ration and eye diagram. The modeling results show very similar trend to the experimental reports.

• Korean Journal of Optics and Photonics
• /
• v.15 no.2
• /
• pp.171-176
• /
• 2004

A light deflector integrated laser diode(LD) was fabricated and the characteristics of LD and ourput beam deflection as a function of deflector injection current were measured. To integrate the deflector with LD, a passive waveguide was integrated with the LD and a triangular-type light deflector was fabricated on the upper clad of the passive waveguide section. Light deflection from the fabricated light deflector is controlled by the effective refractive index variation induced by carrier injection. To characterize the effect of the deflector injection current, threshold current, slope efficiency, and output beam spectrum were measured as a function of deflector injection current. From these measured data, the increment in the threshold current and the decrement of the slope efficiency were observed. However, the output beam spectrum was not affected by the deflector. The Beam Propagation Method(BPM) was used to simulate the proposed device and the light deflection was measured by the far-field pattern of the output beam as a function of the deflector injection current. In the fabricated deflector integrated LD, the deflection angle of 1.9$^{\circ}$ at the injection current of 15 ㎃ was obtained.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.105-105
• /
• 2011

ZnO is a promising material since it could be applied to many fields such as solar cells, laser diodes, thin films transistors and gas sensors. ZnO has a wide and direct band gap for about 3.37 eV at room temperature and a high exciton binding energy of 60 meV. In particular, ZnO features high sensitivity to toxic and combustible gas such as CO, NOX, so on. The development of gas sensors to monitor the toxic and combustible gases is imperative due to the concerns for enviromental pollution and the safety requirements for the industry. In this study, we investigated the effect of substrate temperature and post-annealing on structural and electrical properties of ZnO thin films. ZnO thin films were deposited by pulsed laser deposition (PLD) at various temperatures at from room temperature to $600^{\circ}C$. After that, post-annealing were performed at $600^{\circ}C$. To inspect the structural properties of the deposited ZnO thin films, X-ray diffraction (XRD) was carried out. For gas sensors, the morphology of the films is dominant factor since it is deeply related with the film surface area. Therefore, the atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) were used to observe the surface of the ZnO thin films. Furthermore, we analyzed the electrical properties by using a Hall measurement system.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.48 no.3
• /
• pp.245-254
• /
• 2022

In this study, we tried to investigate the efficacy of combined light therapy using low-power lasers at 655 nm and LEDs emitting wavelengths at 625 ± 5 nm and 850 ± 10 nm in hair loss and scalp. A total of 33 subjects were enrolled in this clinical trial. Each subject used the LLLT and LED device on the scalp for 10 min on a daily basis for 12 weeks. After 12 weeks of LLLT and LED device use, there were significant improvements in redness, elasticity, and hydration of the scalp. Additionally, hair luster and tensile strength were improved. A remarkable decrease in total shed hairs was observed in all subjects at 4, 8, and 12 weeks without any serious adverse event. Combined light therapy using LLLT and LEDs proved to be an effective treatment for reducing hair loss and improving scalp condition.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.4
• /
• pp.130-135
• /
• 1999

The main scale of linear encoder greatly effects on the precision of displacement measurement. Especially when needing the long range measurement the length of main scale should be increased accordingly. In this paper we propose a linear encoder that uses laser interference pattern as main scale for long range measurement. The linear encoder is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase difference of 0. $\pi$/4, $\pi$/2, 3$\pi$/4 are arranged on the panel. The experimental results show that signals of quadratic photo diode A, B, {{{{ {-}atop {A } }}}} and {{{{ {- } atop {B } }}}} are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.