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,...

Efficiency droop in InGaN light-emitting diodes (LEDs) is analyzed based on the rate equation model. By using peak point of efficiency versus current-density relation as parameters analysis, internal quantum and each recombination current at arbitrary density can be unambiguously determined without any knowledge A, B, C coefficients. The theoretical analysis compared with measured a LED sample good agreement between model experiment found. investigation coefficients shows that Auger alone...

Light extraction efficiency (LEE) in AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) is investigated using finite-difference time-domain simulations. For flip-chip and vertical LED structures, LEE obtained to be <10% due strong DUV light absorption the p-GaN layer. In LEDs, of transverse-magnetic (TM) modes found more than ten times smaller that transverse-electric (TE) modes, which explains decreasing behavior external quantum LEDs with wavelength. It also structures can have...

InGaN-based blue and green light-emitting diodes are studied by temperature-dependent electroluminescence (EL) from 300 to 50 K elucidate the effects of carrier overflow saturation in radiative recombination rate on efficiency droop. Severe droop at cryogenic temperatures is attributed overflow, which confirmed EL spectra. The degree thought be related reduced effective active volume subsequent rate. Carrier transport indium clustering region discussed relation volume.

We investigate the effects of current spreading on efficiency droop InGaN blue light-emitting diodes with lateral injection geometry based numerical simulation. Current crowding near mesa edge and decrease in length density are shown to cause significant droop. It is found that can be reduced considerably as uniformity improved by increasing resistivity p-type layer or decreasing sheet resistance n-GaN layer. The reduction well interpreted carrier distribution plane quantum wells.

In InGaN quantum wells (QWs), effective active volume can be greatly reduced due to carrier localization in In-rich region and inhomogeneous distribution. The authors investigate the efficiency droop of InGaN-based light-emitting diodes (LEDs) based on rate equation including influence volume. It is found that characteristics modeled well without employing a large Auger recombination coefficient by assuming only small portion QWs effectively used as region. presented model expected provide...

The efficiency droop in 280-nm AlGaN multiple-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) is analyzed using the carrier rate equation. It shown that internal quantum (ηIQE), injection (ηinj), light-extraction (ηLEE), Shockley–Read–Hall recombination coefficient (A), and Auger (C) can be determined by equation theoretical radiative (B), experimentally measured wavelength spectrum, external (ηEQE). results show spillover from MQWs to p-AlGaN layer main cause of droop.

Abstract For accurate and reliable measurement of the internal quantum efficiency (IQE) light-emitting diodes (LEDs), method should be theoretically solid experimentally simple to use without any prior assumption physical parameters or complicated equipment. In this paper, we critically review conventional characterization techniques for measuring IQE LEDs, including methods based on temperature-dependent electroluminescence constant AB(C) models. After reviewing limitations existing...

At room temperature, AlGaInP pn-junction light-emitting diodes (LEDs) emitting at 630 nm do not exhibit an efficiency droop. However, upon cooling the LEDs to cryogenic temperatures, they show a pronounced We attribute droop in electron-drift-induced reduction injection (i.e., carrier leakage out of active region) mediated by asymmetry pn junction, specifically disparity between electron and hole concentrations mobilities, with concentration exacerbated low temperatures.

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.

Two kinds of green InGaN light emitting diodes (LEDs) have been investigated in order to understand the different slopes logarithmic output power-current (L-I) curves. Through analysis carrier rate equation and by considering density-dependent injection efficiency into quantum wells, L-I curves can be more rigorously understood. The low current level, two as tunneling is initially dominant. high level beyond peak external (EQE) diminishes below one overflow becomes In addition, normalized...

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...

Higher differential quantum efficiency eta /sub df/, smaller chirp Delta lambda , narrower linewidth nu and high coupling C/sub out/ between active passive regions of 1.5 mu m GaInAsP-InP SCH-BIG-DR lasers with a thin layer asymmetric gratings were experimentally demonstrated by comparison those properties distributed feedback (DFB) from the same wafer. A submode suppression ratio (SMSR) more than 39 dB at 1.7 times threshold current almost 100% in indicated that...

We successfully developed a 3D electrical circuit model consisting of resistances and intrinsic diodes to analyze the current spreading effect in an InGaN/GaN multiple-quantum-well light-emitting diode. Each element was formulated by physical parameters such as structural dimensions or material properties. obtained good agreement between measured 2D light intensity distribution emitted from surface fabricated device that calculated with our model. With design tool each epitaxial layer...

The internal electric field due to the piezoelectric effect in an InGaN/GaN multiple quantum-well structure is measured via photoluminescence (PL), electroreflectance (ER), and photocurrent (PC) spectroscopies, measurement results are compared with each other theoretically calculated values. flat-band voltage estimated by measuring applied bias that induces maximum PL peak energy quantum-confined Stark effect, 180° phase shift ER spectrum, smallest band tail state PC spectrum. fields PL, PC,...

While there have been many discussions on the standard Si pn-diodes, little attention has paid and confusion still arises ideality factor of radiative recombination current in semiconductor light-emitting diodes (LEDs). In this letter, we theoretically demonstrate experimentally confirm by using blue infrared LEDs that is unity especially for low-current-density ranges. We utilize data internal quantum efficiency measured temperature-dependent electroluminescence to separate component from...

This study presents an approach for enhancing the external quantum efficiency (EQE) of multiple-quantum-well InGaN/AlGaN near-ultraviolet (NUV) micro-light-emitting diodes (micro-LEDs) without changing epitaxial layer. Unlike size-dependent EQE reduction observed in blue, green, and red micro-LEDs, NUV micro-LEDs at high current densities (≥10 A/cm2) improves as device dimensions shrink from 500 × μm2 to 20 μm2. A micro-LED achieves a peak 12.3%, compared 8.60% larger micro-LED. Experimental...

The effective linewidth enhancement factor alpha /sub eff/ of DFB lasers which have both gain and index coupling coefficients is theoretically analyzed. unique reduction mechanism due to the optical negative feedback modal phase in coupled was found for first time. numerical result showed that can be reduced almost one half material defined when there exists an coefficient comparable coefficient.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML"...

The authors report on the high-performance blue laser diodes (LDs) with an emission wavelength of ~448 nm employing InGaN single-quantum-well (QW) active layers. At 100-mW continuous-wave (CW) output power, operation current and voltage are, respectively, 150 mA 5.3 V, corresponding to wall plug efficiency >12%, a record value for single-mode LDs wavelengths. single QW LD showed normal temperature dependence light output-current curves characteristic 170 K. In addition, we demonstrate high...

Light extraction efficiency (LEE) in thin-film InGaN vertical light-emitting diode (LED) structures with photonic crystal patterns is studied using the three-dimensional finite-difference time-domain simulation. We systematically investigate dependence of LEE on various structural parameters LEDs such as thickness p-GaN and n-GaN layers, air-hole depth size. It found that high > 80% obtainable from unencapsulated for a wide range parameters. In particular, higher observed relatively...

We have grown LED structures on top of a robust n-type GaN template 8-inch diameter silicon substrates achieving both low dislocation density and 7 um-thick without crack even at sufficient Si doping condition. Such high crystalline quality n-GaN templates were obtained by optimizing combination stress compensation layers reduction layers. Wafer bowing well controlled measured below 20 μm the warpage substrate was found to strongly depend initial substrates. The full-width half-maximum...

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...