A5103155316- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- ZnO doping and properties
- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- Ga2O3 and related materials
- Chalcogenide Semiconductor Thin Films
- Semiconductor materials and interfaces
- Electromagnetic Compatibility and Noise Suppression
- Nanowire Synthesis and Applications
- Graphene research and applications
- Photocathodes and Microchannel Plates
- 2D Materials and Applications
- Thin-Film Transistor Technologies
- Multilevel Inverters and Converters
- Organic Light-Emitting Diodes Research
- Quantum Dots Synthesis And Properties
- Superconducting and THz Device Technology
- Silicon and Solar Cell Technologies
- Integrated Circuits and Semiconductor Failure Analysis
Hanyang University
2013-2020
Anyang University
2019
We investigated the optical and electrical properties of red AlGaInP light-emitting diodes (LEDs) as functions chip size, p-cladding layer thickness, number multi-quantum wells (MQWs). External quantum efficiency (EQE) decreased with decreasing size. The ideality factor gradually increased from 1.47 to 1.95 size 350 μm 15 μm. This indicates that smaller LEDs experienced larger carrier loss due Shockley-Read-Hall nonradiative recombination at sidewall defects. S parameter, defined ∂lnL/∂lnI,...
Two kinds of InGaN-based light-emitting diodes (LEDs) are investigated to understand the nonradiative carrier recombination processes. Various temperature-dependent measurements such as external quantum efficiency, current-voltage, and electroluminescence spectra utilized from 50 300 K. Based on these experimental results, we analyze dominant mechanism for each LED device. We also effect efficiency droop. On basis correlation between droop mechanisms, discuss an approach reducing
Local dot-like emissions in InGaN/GaN-based light-emitting diodes under both forward and reverse biases are investigated by carefully examining their locations electroluminescence spectra. The effects of on electrical optical performances also discussed. From the properties leakage-component dependence electric field temperature, dominant leakage mechanism is as a function bias from 100 to 400 K. It concluded that underlying local related threading dislocations biases.
We investigate the current-dependent and temperature-dependent efficiency droops ("J-droop" "T-droop", respectively) in InGaN-based blue AlGaInP-based red light-emitting diodes (LEDs). It is found that LEDs show different droop behaviors with increasing current density temperature. The J-droop significant LED while T-droop severe LED. In case of LED, carrier accumulation caused by saturation radiative recombination rate thought to increase quasi-Fermi level rapidly, thus causing J-droop. On...
We revisited stacking fault identification based on the characteristic photoluminescence emission wavelengths of 4H–SiC epitaxial wafers, and we investigated 50 000 faults in 70 wafers using wafer-level mapping. The spectra each type were obtained analyzed high-angle annular dark-field (HAADF) high-resolution scanning transmission electron microscopy (HR-STEM) targeted faults. Most exhibited specific that converged to wavelength bands when plotting all measured against fault. Regardless...
Frank-type stacking faults in 4H–SiC epitaxial layers were investigated using room-temperature photoluminescence mapping and high-angle annular dark-field high-resolution scanning transmission electron microscopy. Remarkably, the intrinsic fault (5,2) multilayer (4,2), which have been reported to elongated triangular shapes date, found broader shape, was typical shape of Shockley-type faults. The shaping could be explained based on directions partial dislocations bounding Formation models...
Abstract We investigate the nonradiative recombination mechanisms of two conventional InGaN/GaN-based blue light-emitting diodes with different threading dislocation densities (TDDs). The current–voltage, ideality factor, and slope light-versus-current curve on log scales are analyzed to distinguish dominant at room temperature. Through analysis, we infer be Shockley–Read–Hall process for sample a low TDD (∼1 × 10 8 cm −2 ) defect-assisted tunneling high 9 ). For more detailed analysis their...
We present a method of measuring the internal quantum efficiency (IQE) light-emitting diodes (LEDs) as function driving current at an arbitrary temperature only with experimentally measurable quantities optical power and current. The measurement procedure starts to find exact value IQE reference point where injection is considered 100% radiative calculated from infinitesimal change relative external (EQE). Once exactly known, any other by ratio EQE values one. show theoretical formalism...
Abstract In InGaN‐based light‐emitting diodes (LEDs), carrier leakage to the outside of active quantum wells (QWs) has been considered as one dominant loss mechanisms at high current densities. order verify spill‐over phenomenon, we compared electroluminescence (EL) efficiency, resonant photoluminescence (PL) and open‐circuit voltage functions current, temperature, excitation laser power. Very similar tendencies were experimentally observed among three physical quantities, which implied that...
In this study, we aim to understand the thermodynamics inside junctions of GaInN-based LEDs through optical operation device (the wavelength pumping laser is 405 nm for quasi-resonant excitation). First, achieve goal, short-circuit current vs open-circuit voltage curve and photoluminescence spectrum are carefully analyzed compared with current–voltage electroluminescence spectrum. By comparative experimentally demonstrate electrical–optical energy conversion efficiency (ECE) > 100%...
We investigate the current–voltage (I–V) characteristics of InGaN/GaN multiple-quantum-well blue light-emitting diodes (LEDs) to analyze additional voltage drop outside active region. theoretically examine and measure short-circuit current versus open-circuit (ISC–VOC) obtained by photoexcitation compare them with I–V electrical injection. The ISC–VOC curve shows ideal that do not contain deviation from exponential behavior. In ideality factor differentiating curve, increase due series...
In this paper, we aim to understand the interrelationships between current, voltage, radiant power, and eventually, power efficiency (PE) of InGaN-based blue light-emitting diodes (LEDs) at high injection currents. For purpose, first summarize terms definitions various LED efficiencies. It is essential measure each physics behind operation improve device performance further. Here, show how efficiencies with physically measurable quantities spectrum device. Both internal quantum (IQE) voltage...
Two-dimensional (2-D) hexagonal boron nitride (h-BN) has attracted considerable attention for deep ultraviolet optoelectronics and visible single photon sources, however, realization of an electrically-driven light emitter remains challenging due to its wide bandgap nature. Here, we report emission with a red-shift under increasing electric field from few layer h-BN by employing five-period Al2O3/h-BN multiple heterostructure graphene top electrode. Investigation electrical properties...
In InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs), carrier accumulation in MQWs due to the saturation of radiative recombination rate affects internal-quantum-efficiency (IQE) and forward-voltage (VF) characteristics simultaneously. this letter, we investigate interrelation between IQE VF at an operating current density, using 31 blue LEDs with MQW active layers grown under slightly different conditions. The general trend observed demonstrates that decreases as increases....
본 에너지 분산 형 미세열량측정에 관한 자료는 형의 우수한 조작 성을 유지하면서 파장 형과 비슷한 정도의 분해능을 가질 수 있도록 개선한 것으로 광범위한 에너지의 X선을 검출을 할 있다. 검출하기 위해서 이용되는 형은 분해능이 우수하지만 X선의 파장에 대해 검출 각도를 변화시켜야 하고 검출하고자 하는 특정 X선 종류에 따라 몇 가지의 검출기를 필요로 그러나 검출기는 한 개의 검출기로 동시에 검출할 있으며 방법도 비교적 용이하다. 우수하지 못 또한 인접한 에너지를 갖는 X선은 그 피크가 중첩되어 구별하기가 어려운 경우도 분해능은 파장분산 형이 2~20 eV이고 140~180 eV로 상당한 차이가 We have surveyed on microcalorimetry which we can treat with energy dispersive spectrometer(EDS) as wavelength spectrometer(WDS), to be developed in order make...
In InGaN/GaN blue light-emitting diodes (LEDs) widely utilized for general lighting, there exist various material issues that lead to the unwanted nonradiative recombination. this paper, we utilize characterization techniques investigate recombination mechanisms in LED devices. With such as temperature-dependent external quantum efficiency, current-voltage, and electroluminescence spectra, show different processes Shockley-Read-Hall defect-assisted tunneling can play roles Information on...
We investigate the low-frequency noise characteristics of InGaN-based light-emitting diodes with different forward leakage currents. It is found that are closely correlated current.
We investigate the diode ideality factors obtained from photovoltaic characteristics and compare them with ones conventional current-voltage characteristics. By eliminating series resistance in bulk region, measurements can give more accurate information on recombination processes defects active quantum wells.
Using photoluminescence (PL) and high resolution x-ray diffraction (HRXRD) measurements, we study the crystal growth parameters affecting qualities of In/sub x/Ga/sub 1-x/N/GaN multiple quantum wells (MQW), such as GaN barrier thickness, number wells, doping in barriers, so on. Additionally, fabricated blue LEDs using optimized MQW conditions characterized their properties.