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"Diode"

Research Trends on the Hole Transport Layer Interface in Blue Perovskite Light-Emitting Diodes
Seungmin Baek, Donghwan Yun, Gwang Yong Shin, Youngchae Cho, Hyeseon Shin, Mihyun Kim, Harin Kim, Gi-hwan Kim
J Electr Electron Mater 2025;38(6):629-637.   Published online November 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.6.4
Perovskite light-emitting diodes (PELEDs) are emerging as promising candidates for next-generation displays, thanks to their narrow full width at half maximum and low-cost solution processing capabilities. Blue PeLEDs are essential for achieving a full-color gamut; however, efficiency and stability challenges limit their practical use. A primary bottleneck arises from interfacial issues between the perovskite emissive and charge transport layers. This review summarizes the key interfacial challenges hindering the performance of blue PeLEDs and highlights recent advances in interfacial engineering strategies. By focusing on interfacial engineering between the hole-transport layer and perovskite, this review compares different strategies and outlines future directions for developing high-performance blue light-emitting devices.
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Recent Advances in Charge Generation Layer Design for Tandem Quantum Dot Light-Emitting Diodes
Eui Chang Jung, Moon Kee Choi
J Electr Electron Mater 2025;38(6):593-603.   Published online November 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.6.1
Quantum dots (QDs) offer size-dependent tunability across the infrared to ultraviolet range with narrow emission linewidths and high color purity, making them highly attractive for next-generation light-emitting devices. Quantum dot lightemitting diodes (QLEDs) further combine precise spectral control with scalable, low-cost solution processing, positioning them as strong candidates for wearable, stretchable, and AR/VR display technologies. However, conventional single-emission QLEDs suffer from charge imbalance, efficiency roll-off, and limited operational lifetime, necessitating new device architectures. Tandem QLEDs, which vertically stack multiple emissive layers (EMLs) connected by charge generation layers (CGLs), provide a compelling solution by enabling higher luminance, improved charge balance, and longer lifetime at equivalent current density. The CGL serves as the interfacial region mediating charge injection and generation between adjacent EMLs, directly determining device efficiency and stability. This review highlights recent progress in CGL engineering, categorizing representative designs into planar heterojunction, inorganic-based, and dipole-based configurations. Comparative analysis of their formation mechanisms, material systems, and process compatibilities reveals evolving charge-control strategies that extend beyond material selection. These insights establish design principles for next-generation tandem QLEDs with enhanced efficiency, durability, and manufacturability.
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Electrical Characterization of Ga₂O₃/4H-SiC Schottky Diodes Using Aerosol Deposition Method
Ji-hyun Kim, Ye-jin Kim, Seung-hyun Park, Chang-jun Park, Jong-min Oh, Weon Ho Shin, Chulhwan Park, Sang-mo Koo
J Electr Electron Mater 2025;38(5):499-505.   Published online September 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.5.4
Ga₂O₃ is an ultra-wide bandgap semiconductor material that offers superior electrical properties for high-voltage power electronics but suffers from poor thermal conductivity compared to conventional semiconductors. To overcome this thermal limitation, we developed Ga₂O₃/4H-SiC heterojunction Schottky barrier diodes that utilize the high thermal conductivity of SiC substrates. Using the aerosol deposition method, we successfully fabricated devices with different Ga₂O₃ film thicknesses (0.8-1.4 μm) and achieved exceptional electrical performance with the 0.8 μm device showing a specific on-resistance of 41 mΩ·cm² and a leakage current as low as 1.26 × 10-10 A/cm² while maintaining stable operation up to 200℃. The devices demonstrated breakdown voltages reaching 2,365 V and maintained excellent rectification ratios above 1010 even at elevated temperatures. All fabricated devices with different film thicknesses showed consistent high-temperature stability, confirming the effectiveness of the heterojunction approach. These results provide a viable pathway for developing thermally stable, high-performance power devices essential for next-generation electric vehicle and renewable energy applications
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Cathodoluminescence (CL) spectroscopy provides valuable insights into the optical and electronic properties of materials by analyzing photon emission induced by electron beam excitation. In this study, we present a novel CL detection system integrated into a transmission electron microscope (TEM) specimen stage, enabling high-resolution optical analysis of internal microstructures. The system features a parabolic mirror, a focusing lens, and a UV-VIS range optical fiber to maximize light collection and transmission efficiency, with performance further enhanced by a liquid nitrogen cooling setup. Using this system, we successfully performed CL mapping of InGaN/GaN multiple quantum wells (MQWs) and GaN thin films. The results revealed that threading dislocations act as non-radiative centers in GaN and locally increase the bandgap energy in InGaN MQWs, causing a blue-shift in CL emission. These findings support a model in which dislocations induce carrier delocalization, preserving high radiative efficiency despite high dislocation densities. This work demonstrates the effectiveness of the TEM-integrated CL system for nanoscale optical characterization, offering a new pathway for studying defect-related phenomena in semiconductor materials.
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Factors Limiting Power Conversion Efficiency in GaInN/GaN-Based μ-LEDs Investigated by Chip-Size and Temperature-Dependent Measurements
Hana Lim, Jiye Choi, Minji Ryu, Yejin Kim, Ilji Hwang, Dong-pyo Han
J Electr Electron Mater 2025;38(3):282-289.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.7
This study aimed to elucidate factors limiting power conversion efficiency (PCE) in GaN-based micro-light-emitting diodes (μ-LEDs). To this end, we investigated the effects of operating temperature and chip-size of μ-LEDs on their efficiency. For the investigation, 460 nm-emitting μ-LEDs with various chip-sizes were fabricated; then their characteristics were carefully measured from 100 to 400 K. As the chip-size decreases and the operating temperature increases, their PCE and external quantum efficiency (EQE) decrease, while voltage efficiency (VE) increases. This indicates that the EQE plays a more important role than the VE in determining the PCE of μ-LEDs. Particularly, for a chip-size of 20 × 20 μm2, the EQE was very lower and the ideality factor was unexpectedly higher compared to the others for all operating temperatures, which is believed to be due to the critical plasma damage at the sidewall during dry-etching process for the chip-size < 20 × 20 μm2.
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Optimization of the P+ Region in SiC-Based MPS Diodes: Enhancing BFOM and Alleviating Snap-Back Phenomenon
Seung-hyun Park, Tae-hee Lee, Se-rim Park, Ju-eun Yun, Geon-hee Lee, Ji-hwan Jeon, Jong-min Oh, Weon Ho Shin, Sang-mo Koo
J Electr Electron Mater 2024;37(6):675-679.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.15
Department of Electric Materials Engineering, Kwangwoon University, Seoul 01897, Korea (Received June 13, 2024; Revised July 8, 2024; Accepted July 10, 2024) Abstract: Wide bandgap (WBG) devices, especially SiC, are gaining traction as materials for high-power EV conversion devices due to their superior efficiency and switching capabilities compared to Si-based power devices. SiC allows for high power, high temperature, and high frequency applications because of its outstanding thermal conductivity, saturation velocity, and dielectric breakdown field. SiC-based MPS diodes combine the advantages of SiC-based SBDs and PiN diodes, allowing high-frequency switching operation with low leakage currents under high voltage conditions. However, MPS diodes exhibit snapback phenomena influenced by the P+ region’s size, necessitating optimization. A TCAD simulation studied the impact of the P+ region’s depth and width on MPS diode performance. Increasing the P+ width raised the On-specific resistance (Ron,sp) and lowered the maximum voltage during snapback (Vsnap). Increasing the depth decreased both Breakdown voltage (BV) and Vsnap. A trade-off between the semiconductor performance index BFOM and Vsnap was identified, leading to optimized dimensions. The optimized MPS diode shows a low Vsnap of about 3.89 V and a high BFOM of 1.72 GW·㎠, highlighting its potential as a next-generation high-performance power conversion device.
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Thermal Management Impact of Heat Conductive Layers on Ga₂O₃ Schottky Barrier Diodes
Ye-jin Kim, Geon-hee Lee, Min-yeong Kim, Se-rim Park, Seung-hwan Chung, Sang-mo Koo
J Electr Electron Mater 2024;37(6):657-661.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.12
Gallium oxide (Ga₂O₃) is emerging as a next-generation power semiconductor material due to its excellent electrical properties, including an ultra-wide bandgap of approximately 4.8 eV and a breakdown electric field of about 7 MV/cm. However, its low thermal conductivity of around 0.13 W/cmK presents significant challenges to the performance and reliability of Ga₂O₃- based devices. In this study, we employed the Silvaco TCAD simulator to analyze the thermal and electrical characteristics of Ga₂O₃ Schottky barrier diodes (SBDs) with heat sinks of varying thermal conductivities. The results demonstrate that heat sinks with higher thermal conductivity effectively mitigate the temperature rise in the device, leading to an increase in current density. The limitation in heat dissipation due to parasitic on-state resistance not only affects device performance but also impacts longterm reliability. Therefore, this study contributes to the development of effective thermal management strategies for Ga₂O₃-based power semiconductors.
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Micro Light-Emitting Diodes with 3D-Printed Hydrogel Microlens for Optical Property Enhancements
Yujin Ko, Jeong Hyeon Kim, Sang Yoon Park, Kang Hyeon Kim, Seong Min Hong, Bo-yeon Lee, Han Eol Lee
J Electr Electron Mater 2024;37(5):554-561.   Published online September 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.5.13
Micro light-emitting diodes (μLEDs) have been utilized in various fields such as displays, and smart devices, due to their superior stabilities. Since the applications of the μLEDs have been extended to medical devices and wearable sensors, excellent optical properties and uniformity of the μLEDs are important. Hence, several researchers have investigated to enhance the optical efficiency of the μLEDs through micro/nano lens. However, the reported methods for realizing the micro/nano lens have some drawbacks such as complex and high-cost manufacturing processes. Herein, we developed μLEDs with 3D-printed hydrogel microlenses. The printed hydrogel had high transparency and excellent adhesive strength, allowing it to attach onto top surface of the μLEDs without any additional adhesives. Microscale printing technology using a 3D printer achieved quick and fine printing in desired shapes and arrangements, showing the possibility of mass production. The 3D-printed microlens can be applied to improve not only the optical properties of μLEDs but also other optical devices.
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Comparison of Electrical Properties of β-Gallium Oxide (β-Ga2O3) Power SBDs with Guard Ring Structures
Hoon-ki Lee, Kyujun Cho, Woojin Chang, Jae-kyoung Mun
J Electr Electron Mater 2024;37(2):208-214.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.13
This reports the electrical properties of single-crystal β-gallium oxide (β-Ga2O3) vertical Schottky barrier diodes (SBDs) with a different guard ring structure. The vertical Schottky barrier diodes (V-SBDs) were fabricated with two types guard ring structures, one is with metal deposited on the Al2O3 passivation layer (film guard ring: FGR) and the other is with vias formed in the Al2O3 passivation layer to allow the metal to contact the Ga2O3 surface (metal guard ring: MGR). The forward current values of FGR and MGR V-SBD are 955 mA and 666 mA at 9 V, respectively, and the specific on-resistance (Ron,sp) is 5.9 mΩ·cm2 and 29 mΩ·cm2. The series resistance (Rs) in the nonlinear section extracted using Cheung’s formula was 6 Ω, 4.8 Ω for FGR V-SBD, 10.7 Ω, 6.7 Ω for MGR V-SBD, respectively, and the breakdown voltage was 528 V for FGR V-SBD and 358 V for MGR V-SBD. Degradation of electrical characteristics of the MGR V-SBD can be attributed to the increased reverse leakage current caused by the guard ring structure, and it is expected that the electrical performance can be improved by preventing premature leakage current when an appropriate reverse voltage is applied to the guard ring area. On the other hand, FGR V-SBD shows overall better electrical properties than MGR V-SBD because Al2O3 was widely deposited on the Ga2O3 surface, which prevent leakage current on the Ga2O3 surface.
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Advances in Intrinsically Stretchable Light-Emitting Diodes
Wonjin Koh, Moon Kee Choi
J Electr Electron Mater 2023;36(6):537-546.   Published online November 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.6.1
Intrinsically stretchable light-emitting diodes, composed of stretchable electrodes, charge transport layers, and luminescent materials, have garnered significant interest for enhancing human well-being and advancing the field of deformable electronics. Various luminescent materials, such as perovskites and organics, have been integrated with stretchable elastomers to function as the stretchable emissive layers in these intrinsically stretchable LEDs. Stretchable conductors including Ag nanowire based percolating structures and conducting polymers have been utilized as stretchable transparent electrode. Despite this progress, their performances in terms of efficiency and stability remain challenging compared to their structurally stretchable and rigid LED counterparts. This review offers a comprehensive overview of recent advancements in intrinsically stretchable LEDs, focusing on material innovations.
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Vertical β-Ga2O3 Schottky Barrier Diodes with High-κ Dielectric Field Plate
Se-rim Park, Tae-hee Lee, Hui-cheol Kim, Min-yeong Kim, Soo-young Moon, Hee-jae Lee, Dong-wook Byun, Geon-hee Lee, Sang-mo Koo
J Electr Electron Mater 2023;36(3):298-302.   Published online May 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.3.14
In this paper, we discussed the effect of field plate dielectric materials such as silicon dioxide (SiO2), aluminum oxide (Al2O3), and hafnium oxide (HfO2) on the breakdown characteristics of β-Ga2O3 Schottky barrier diodes (SBDs). The breakdown voltage (BV) of the SBDs with a field plate was higher than that of SBDs without a field plate. The higher dielectric constant of HfO2 contributed to the superior reduction in electric field concentration at the Schottky junction edge from 5.4 to 2.4 MV/cm. The SBDs with HfO2 field plate showed the highest BV of 720 V, and constant specific on-resistance (Ron,sp) of 5.6 mΩ·㎠, resulting in the highest Baliga’s figure-of-merit (BFOM) of 92.0 MW/㎠. We also investigated the effect of dielectric thickness and field plate length on BV.
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Electrical Characteristics Analysis Depending on the Portion of MPS Diode Fabricated Based on 4H-SiC in Schottky Region
Hyung-jin Lee, Ye-hwan Kang, Seung-woo Jung, Geon-hee Lee, Dong-wook Byun, Myeong-choel Shin, Chang-heon Yang, Sang-mo Koo
J Electr Electron Mater 2022;35(3):241-245.   Published online May 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.3.5
In this study, we measured and comparatively analyzed the characteristics of MPS (Merged Pin Schottky) diodes in 4H-SiC by changing the areal ratio between the Schottky and PN junction region. Increasing the temperature from 298 K to 473 K resulted in the threshold voltage shifting from 0.8 V to 0.5 V. A wider Schottky region indicates a lower on-resistance and a faster turn-on. The effective barrier height was smaller for a wider Schottky region. Additionally, the depletion layer became smaller under the influence of the reduced effective barrier height. The wider Schottky region resulted in the ideality factor being reduced from 1.37 to 1.01, which is closer to an ideal device. The leakage saturation current increased with the widening Schottky region, resulting in a 1.38 times to 2.09 times larger leakage current.
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Deep Level Defect Transient Spectroscopy Analysis of 4H-SiC SBD and JBS Diodes
Dong-wook Byun, Myeong-cheol Shin, Jeong Hyun Moon, Wook Bahng, Weon Ho Shin, Jong-min Oh, Chulhwan Park, Sang-mo Koo
J Electr Electron Mater 2021;34(3):214-219.   Published online May 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.3.9
We investigated deep levels in n-type 4H-SiC epitaxy layer of the Schottky barrier diodes (SBD) and Junction Barrier Schottky (JBS) diodes by using deep level transient spectroscopy (DLTS). The I-V characteristics of the JBS devices show ~100 times lower leakage current level than SBDs owing to the grid structures in JBS. The reliable responses of the diodes for deep level transient analysis showed from C-V characteristics. Several deep electron traps were revealed by DLTS measurements in epitaxial layers in 4H-SiC. In both types of diodes, the peaks corresponding to shallow energy levels were observed with slightly different values of 0.132 eV for JBS and 0.186 eV for SBDs. The two remarkable deep level peaks (J2 and J3) have been obtained with 0.257 eV and 0.273 eV in JBS, and they were analyzed to have a similar trap concentration of ~1014 cm-3. The comparison results showed that the defects could be related with device fabrication procedures such as ion-implantation and growth.
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Characteristics of Ga2O3/4H-SiC Heterojunction Diode with Annealing Process
Young-jae Lee, Sang-mo Koo
J Electr Electron Mater 2020;33(2):155-160.   Published online March 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.2.15
Ga2O3/n-type 4H-SiC heterojunction diodes were fabricated by RF magnetron sputtering. The optical properties of Ga2O3 and electrical properties of diodes were investigated. I-V characteristics were compared with simulation data from the Atlas software. The band gap of Ga2O3 was changed from 5.01 eV to 4.88 eV through oxygen annealing. The doping concentration of Ga2O3 was extracted from C-V characteristics. The annealed oxygen exhibited twice higher doping concentration. The annealed diodes showed improved turn-on voltage (0.99 V) and lower leakage current (3 pA). Furthermore, the oxygen-annealed diodes exhibited a temperature cross-point when temperature increased, and its ideality factor was lower than that of as-grown diodes.
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Quantum Dot Light-Emitting Diodes with Poly-TPD/PVK Bilayer Hole Transport Layer
Hyun Soo Kim, Do Hyung Lee, Bada Kim, Bo Ram Hwang, Chang Kyo Kim
J Electr Electron Mater 2019;32(5):393-398.   Published online September 1, 2019
A poly[bis(4-butypheny)-bis(phenyl)benzidine] (poly-TPD) and poly(9-vinylcarbazole) (PVK) bilayer was employed as a hole transport layer (HTL) in solution-processed CdSe/ZnS quantum dot light-emitting diodes (QLEDs). The thickness of the PVK layer spin-coated onto the poly-TPD layer, whose thickness was fixed to 40 nm, was varied, with PVK layer thicknesses of 0 nm, 35 nm, 45 nm, and 55 nm. Because the thickness of the PVK can determine the hole transport properties of the HTL, a PVK thickness that maximizes the performance of the HTL for the QLEDs was investigated. By employing the optimized PVK thickness of 45 nm, the current efficiency of the QLED exhibited a 1.74 times improvement when compared with that of the QLED with poly-TPD based HTL without PVK. This was mainly attributed to the decrease in the energy barrier between the HTL and the quantum dot (QD) emitting layer (EML).
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Chip Size-Dependent Light Extraction Efficiency for Blue Micro-LEDs
Hyun Jung Park, Yu-jung Cha, Joon Seop Kwak
J Electr Electron Mater 2019;32(1):47-52.   Published online January 1, 2019
Micro-LEDs show lower efficiencies compared to general LEDs having large areas. Simulations were carried out using ray-tracing software to investigate the change in light extraction efficiency and light distribution according to chip-size of blue flip-chip micro-LEDs (FC μ-LEDs). After fixing the height of the square FC μ-LED chip at 158 μm, the length of one side was varied, with dimensions of 2, 5, 10, 30, 50, 100, 300, and 500 μm. The highest light-extraction efficiency was obtained at 10 μm, beyond which the efficiency decreased as the chip-size increased. The chip size-dependence of the FC μ-LEDs both without the patterned sapphire substrate, as well as vertical FC μ-LEDs, were analyzed.
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Fully Solution-Processed Green Organic Light-Emitting Diodes Using the Optimized Electron Transport Layers
Joo Won Han, Yong Hyun Kim
J Electr Electron Mater 2018;31(7):486-489.   Published online November 1, 2018
Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.
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Electrical Characteristics of 4H-SiC Junction Barrier Schottky Diode
Young-jae Lee, Seulki Cho, Ji-ho Seo, Seong-ji Min, Jae-in An, Jong-min Oh, Sang-mo Koo, Deaseok Lee
J Electr Electron Mater 2018;31(6):367-371.   Published online September 1, 2018
1,200 V class junction barrier schottky (JBS) diodes and schottky barrier diodes (SBD) were simultaneously fabricated on the same 4H-SiC wafer. The resulting diodes were characterized at temperatures from room temperature to 473 K and subsequently compared in terms of their respective I-V characteristics. The parameters deduced from the observed I-V measurements, including ideality factor and series resistance, indicate that, as the temperature increases, the threshold voltage decreases whereas the ideality factor and barrier height increase. As JBS diodes have both Schottky and PN junction structures, the proper depletion layer thickness, Ron, and electron mobility values must be determined in order to produce diodes with an effective barrier height. The comparison results showed that the JBS diodes exhibit a larger effective barrier height compared to the SBDs.
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The Effects of Lithium-Incorporated on N-ZTO/P-SiC Heterojunction Diodes by Using a Solution Process
Hyun-soo Lee, Sung-joon Park, Jae-in An, Seulki Cho, Sang-mo Koo
J Electr Electron Mater 2018;31(4):203-207.   Published online May 1, 2018
In this work, we investigate the effects of lithium doping on the electric performance of solution-processed n-type zinc tin oxide (ZTO)/p-type silicon carbide (SiC) heterojunction diode structures. The proper amount of lithium doping not only affects the carrier concentration and interface quality but also influences the temperature sensitivity of the series resistance and activation energy. We confirmed that the device characteristics vary with lithium doping at concentrations of 0, 10, and 20 wt%. In particular, the highest rectification ratio of 1.89×107 and the lowest trap density of 4.829×1,022 cm-2 were observed at 20 wt% of lithium doping. Devices at this doping level showed the best characteristics. As the temperature was increased, the series resistance value decreased. Additionally, the activation energy was observed to change with respect to the component acting on the trap. We have demonstrated that lithium doping is an effective way to obtain a higher performance ZTO-based diode.
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Enhancement of Electrical Properties of Organic Light-Emitting Diodes Using F4-TCNQ Molecule as a Hole-Transport Layer
Su Hwan Na, Won Jae Lee
J Electr Electron Mater 2017;30(11):717-721.   Published online November 1, 2017
We studied the performance enhancement of organic light-emitting diodes (OLEDs) using 2,3,5,6-fluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) as the hole-transport layer. To investigate how F4-TCNQ affects the device performance, we fabricated a reference device in an ITO (170 nm)/TPD(40 nm)/Alq3(60 nm)/LiF(0.5 nm)/Al(100 nm) structure. Several types of test devices were manufactured by either doping the F4-TCNQ in the TPD layer or forming a separate F4-TCNQ layer between the ITO anode and TPD layer. N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD), tri(8-hydroxyquinoline) aluminum (Alq3), and F4-TCNQ layers were formed by thermal evaporation at a pressure of 10-6 torr. The deposition rate was 1.0-1.5 Å/s for TPD and Alq3. The LiF was subsequently thermally evaporated at a deposition rate of 0.2 Å/s. The performance of the OLEDs was considered with respect to the turn-on voltage, luminance, and current efficiency. It was found that the use of F4-TCNQ in OLEDs enhances the performance of the device. In particular, the use of a separate layer of F4-TCNQ realizes better device performance than other types of OLEDs.
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Silver Nanowire-Based Stretchable Transparent Electrodes for Deformable Organic Light-Emitting Diodes
Hyunsu Jung, Hyeck Go, Gye-choon Park, Changhun Yun
J Electr Electron Mater 2017;30(10):609-614.   Published online October 1, 2017
The proposed stretchable transparent electrodes based on silver nanowires (AgNWs) were prepared on a polyurethane (PU) substrate. In order toavoid the surface roughness caused by the silver nanowires, a titanium oxide (TiO2) buffer layer was addedby coating and heating the organometallic sol-gel solution. The fabricated stretchable electrodes showedan electrical sheet resistance of 24 Ωsq-1, 78% transmittance at 550 nm, and an average surface roughness below 5 nm. Furthermore, the AgNW-based electrode maintained its initial electrical resistance under 130% strain testing conditions, without the assistance of additional conductive polymer layers. In this paper, the critical role of the TiO2 buffer layer between the AgNW network and the PU substrate has been discussed.
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Study on the Design of Power MOSFET with ESD Protection Circuits
Eui Seok Nahm, Ey Goo Kang
J Electr Electron Mater 2015;28(9):555-560.   Published online September 1, 2015
This paper was proposed 900 V Power MOSFET with ESD protection circuits using zener diodes. And we were carried out and analyzed its electrical characteristics. As a result of designing 900 V power MOSFET, we obtained 1,000 V breakdown voltage, 3.49 V threshold voltage and 0.249 Ω·cm2. And we designed ESD circuits using 2 series zener diode and 4 series zener diodes. After analyzing electrical characteristics, we obtained 26 V forward voltage drop and 47 V breakdown voltage. Therefore, This devices can enoughly use power module, SMPS and Automotive.
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Light Source and Application Technology : Design and Fabrication of Heat Sink for Vehicle LED Headlamp Using Thermally-Conductive Plastics
Hyeong Jin Kim, Dong Kyu Lee, Hyun Jung Park, Hoe Seok Yang, Pil Sun Na, Joon Seop Kwak
J Electr Electron Mater 2015;28(8):544-549.   Published online August 1, 2015
Since LEDs (light emitting diodes) have many advantages as a light source in vehicle headlamp, such as good reliability, energy and space saving, and flexible headlamp design. On the other hand, the dependence of its performance and life on temperature have great influence on its practical use. In this study, design and fabrication of heat sink for vehicle LED headlamp were performed using thermally-conductive plastics. This study focused on the effective heat sink structure with limited space in the vehicle LED headlamp. We designed two different prototype of heat sink by thermal simulation using SolidWorks program, which had excellent temperature characteristics. The two different prototype of heat sink were fabricated by injection molding with thermally-conductive plastics. The results showed that LED Tj (junction temperature) of sample B (model 1) and sample C (model 1, 2) was below then 165℃ when applying the thermally-conductive plastics in heat sink of vehicle LED headlamp.
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A Study on the Improvement of Light-Extraction Efficiency of Organic Light-Emitting Diodes with a Use of Random-Textured Film
Hye Sook Kim, Deok Hyeon Hwang, Kyeong Uk Jang, Tae Wan Kim
J Electr Electron Mater 2015;28(7):446-449.   Published online July 1, 2015
An improvement of light-extraction efficiency of organic light-emitting diodes was studied by using random-textured films (RTF). Device was made in a structure of RTF/glass/ITO/TPD/Alq3/LiF/Al. RTF mold was made by spreading PDMS solution on a sandpaper. By pressing this mold on the glass substrate pre-coated with ZPU material, the RTF was obtained. From this study, there was an improvement of external quantum efficiency by about 30% in the device with the random-textured film (RTF 40) compared to that of the reference one.
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Trends of Deep UV-LED Technology for the Pathogen and Biotoxin Aerosol Detection System
Eugene Chong, Young Su Jeong, Kibong Choi
J Electr Electron Mater 2015;28(5):277-284.   Published online May 1, 2015
The humans are under attack involving the hazardous environment and pathogen/biotoxin aerosol that is realistic concerned. A portable, fast, reliable, and cheap Pathogen and Biotoxin Aerosol threat Detection(PBAD) trigger is an important technology for detect-to-protect and detect-to-treat system because the man-made biological terror is a fast and lethal infection. The ultraviolet C(UVC) wavelengths light source is key issue for PBAD that is sensitive because of strong fluorescence cross section from fluorescent amino acids in proteins such as tryptophan and tyrosine. The UVC-light emitting diode(LED) is emerging light source technology as alternative to laser or lamps as they offer several advantages. This paper discussed about the design consideration of UVC-LED for the PBAD system. The UVC-LED and PBAD technology, currently available or in development, are also discussed.
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Light Source and Application Technology : An Efficiency Improvement of the OLEDs due to the Thickness Variation on Hole-Iniection Materials
Jong Yeol Shin, Yi Wei Guo, Tae Wan Kim, Jin Woong Hong
J Electr Electron Mater 2015;28(5):344-349.   Published online May 1, 2015
A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/Alq3/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/Alq3/BCP/Lif/Al were studied experimentally.
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Regular Paper : Semiconductor ; Temperature Dependence of Neutron Irradiated SiC Schottky Diode
Sung Su Kim, Sang Mo Koo
J Electr Electron Mater 2014;27(10):618-622.   Published online October 1, 2014
The temperature dependent characteristics on the properties of SiC Schottky Diode has beeninvestigated. In this study, the temperature dependent current-voltage characteristics of the SiC Schottkydiode were measured in the range of 300 ∼ 500 K. Divided into pre- and post- irradiated device wasmeasured. The barrier height after irradiation device at 500 K increased 0.15 eV compared to 300 K, thebarrier height of pre- neutron irradiated Schottky diode increased 0.07 eV. The effective barrier heightafter irradiation increased from 0.89 eV to 1.05 eV. And ideality factor of neutron irradiated Schottkydiode at 500 K decreased 0.428 compared to 300 K, the ideality factor of pre- neutron irradiated Schottkydiode decreased 0.354. Also, a slight positive shift in threshold voltage from 0.53 to 0.68 V. we analyzedthe effective barrier height and ideality factor of SiC Schottky diode as function of temperature.
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Light Source and Application Technology : A Study on the Application of LED at Ultra-low Temperature
Hee Ju Ha, Jin Wook Kim, Sun Jae Kim, Gyung Suk Kil
J Electr Electron Mater 2014;27(9):600-605.   Published online September 1, 2014
The interest in development on luminaires which are available up to -52℃ is surging as demands in vessels navigating a north pole route increase. A conventional incandescent lamp used invessels is operated stably at -52℃, but many countries including Korea have eliminated the use of incandescent lamps gradually because of its low luminous efficacy. In this paper, therefore, to develop the LED luminaires with high-efficiency, long lifetime that enables to substitute for incandescent lamp, it has studied about cryogenic characteristics of LED packages, bulbs, driving circuit and power supply. This experiments were carried out according to standards IEC 60945-8.4.1. Temperature range is from -60℃ to25℃, and the light output depending on ambient temperature. It showed that, based on 25℃, light output of a CFL decreased by 80% of CFL at -20℃ while each increased 12% of LED bulbs and 16∼19% of LED packages at -60℃.
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Light Source and Application Technology : A Study on a Novel LED Lighting Fixture for Crosswalk Having Two Different Light Distributions
Hyeong Jin Kim, Dong Kyu Lee, Joon Seop Kwak
J Electr Electron Mater 2014;27(9):606-611.   Published online September 1, 2014
Recently, LED lighting fixtures for crosswalk become popular in order to recognize the pedestrians at crosswalk, which can enhance the safety of the pedestrian at crosswalk. However, there are several problems related to the LED lighting fixtures for crosswalk, such as a lot of energy consumption due to a constant illumination during night and glaring of pedestrians at the opposite side of crosswalk. In this study, in order to overcome these problems, we have investigated a novel LED lighting fixture for crosswalk, which has two modules with different angles (60°, 120°). Illuminance of min and max at four-line city street crosswalk shown 50 Lux, 125 Lux, respectively. Illuminance of min and max at eight-line city street crosswalk shown 150 Lux, 200 Lux, respectively. Simulation investigation was optimized design using optical program. Prototype was verified measurement by goniometer system.
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The Effect of Neutron Radiation on the Electrical Characteristics of SiC Schottky Diodes
Sung Su Kim, Min Seok Kang, Man Soon Cho, Sang Mo Koo
J Electr Electron Mater 2014;27(4):199-202.   Published online April 1, 2014
The effect of neutron irradiation on the properties of SiC Schottky Diode has been investigated. SiC Schottky diodes were irradiated under neutron fluences and compared to the reference samples to study the radiation-induced changes in device properties. The condition of neutron irradiation was 3.1×1010n/cm2. The current density after irradiation decreased from 12.7 to 0.75 A/cm2. Also, a slight positive shift (ΔVth= 0.15 V) in threshold voltage from 0.53 to 0.68 V and a positive change (ΔΦB= 0.16 eV) of barrier height from 0.89 to 1.05 eV have been observed by the neutron irradiation, which is attributed to charge damage in the interface between the metal and the SiC layer.
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