共查询到20条相似文献,搜索用时 15 毫秒
1.
V. E. Kudryashov S. S. Mamakin A. N. Turkin A. É. Yunovich A. N. Kovalev F. I. Manyakhin 《Semiconductors》2001,35(7):827-834
Luminescence spectra and quantum yield in light emitting diodes (LEDs) based on InGaN/AlGaN/GaN heterostructures with multiple
quantum wells (MQWs) were studied in the range of currents J=10−6–10−1 A. Minor spread in the quantum yield at operating currents (±15% at J≈10 mA) was observed in these LEDs, which were fabricated by Hewlett-Packard. The spread is due to differences in the current
and voltage dependences of the diode emission intensity, caused by differences in the charged center distribution across the
space-charge region (SCR) of the structures and in the role of the tunnel current component at low voltages. In the diodes
with a thin (≲120 nm) SCR, a tunnel emission band was observed for J≲100 μA; the peak energy of this band ℏωmax=1.92–2.05 eV corresponds to the voltage applied. At low currents (J=0.05–0.5 mA), the spectral position of the main peak ℏωmax=2.35–2.36 eV is independent of the voltage and is determined by the radiative transitions between the localized states. At
J>1 mA, this band shifts with the current (ℏωmax=2.36–2.52 eV). Its shape corresponds to the model for the occupation of states in the two-dimensional energy band tails,
which are caused by the microscopic potential fluctuations. The four parameters in this model are related to the calculated
energy band diagram of the MQW structure.
__________
Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 7, 2001, pp. 861–868.
Original Russian Text Copyright ? 2001 by Kudryashov, Mamakin, Turkin, Yunovich, Kovalev, Manyakhin.
Part of this study was reported at the 3rd All-Russia Workshop on Structures and Devices Based on Gallium, Indium, and Aluminum
Nitrides (Moscow State University, 1999); the 3rd International Conference on Nitride Semiconductors (Montpellier, 1999);
and the 4th European Gallium Nitride Workshop (Nottingham, 2000). 相似文献
2.
Hwan Hee Jeong Kwang Ki ChoiJune-O Song Jung-Hee LeeTae-Yeon Seong 《Microelectronic Engineering》2011,88(10):3164-3167
The light output and electrical characteristics of GaN-based vertical light emitting diodes were investigated as a function of n-GaN thickness. The forward voltage increases from 3.34 to 3.42 V at an injection current of 350 mA as the n-GaN thickness decreases from 5.0 to 2.0 μm. Even at a high injection current of 2.0 A, LEDs with 2.0 μm-thick n-GaN reveal stable forward characteristics which are comparable to those of LEDs with 5.0 μm-thick n-GaN. All the samples exhibit almost the same reverse current up to approximately −8 V. The output power increases with decreasing n-GaN layer thickness. For example, LEDs with 2.0 μm-thick n-GaN yield about 12% higher light output power as compared to LEDs with 5.0 μm-thick n-GaN. Their light output power continuously increases without saturation as the injection current increases up to 1 A. The n-GaN thickness dependence of the electrical characteristics is described and discussed. 相似文献
3.
Xuejiao Sun Zhiguo Yu Ning Zhang Lei Liu Junxi Wang Jinmin Li Yun Zhang 《半导体学报》2019,40(3):032301-032301-4
Metallic nanotextured reflectors have been widely used in light emitting diodes (LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however, only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference time-domain (FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon (SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices. 相似文献
4.
Periyayya Uthirakumar Ji Hye Kang Beo Deul Ryu Chang-Hee Hong 《Materials Science in Semiconductor Processing》2010,13(5-6):329-332
Light extraction efficiency of GaN-based light emitting diodes (LEDs) has improved significantly by using ITO/ZnO layer texturing. We have deliberately designed and successfully fabricated GaN-based LEDs having one and two interfaces of ITO/ZnO layer texturing in the device structure. It was found that the light extraction efficiencies of one and two interfaces of ITO/ZnO-layer texturing LEDs were 22.29% and 35.54% at 20 mA of current injection, respectively. Creating the chances of multiple light scattering at more than one interface is playing a major role to enhance light output power of the device. The source of the enhanced light output power is also discussed. 相似文献
5.
Yang Hua Wang Xiaofeng Ruan Jun Li Zhicong Yi Xiaoyan Duan Yao Zeng Yiping Wang Guohong 《半导体学报》2009,30(9):094002-094002-4
preading layers are analyzed. 相似文献
6.
Nano-hole patterned sapphire substrates (NHPSSs) were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography (LIL) combined with reactive ion etching (RIE) and inductively coupled plasma (ICP) techniques. Gallium nitride (GaN)-based light emitting diode (LED) structure was grown on NHPSS by metal organic chemical vapor deposition (MOCVD). Photoluminescence (PL) measurement was conducted to compare the luminescence efficiency of the GaN-based LED structure grown on NHPSS (NHPSS-LED) and that on unpatterned sapphire substrates (UPSS-LED). Electroluminescence (EL) measurement shows that the output power of NHPSS-LED is 2.3 times as high as that of UPSS-LED with an injection current of 150 mA. Both PL and EL results imply that NHPSS has an advantage in improving the crystalline quality of GaN epilayer and light extraction efficiency of LEDs at the same time. 相似文献
7.
Gallium nitride (GaN) based light emitting diodes (LEDs) with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy (MVPE) are fabricated successfully. Compared with GaN-based LEDs employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEDs show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO (002) ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LED. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEDs with ZnO transparent current spreading layers are analyzed. 相似文献
8.
In this letter, lateral GaN-based Light Emitting Diodes (LEDs) with a SiO2 current blocking layer (CBL) buried in the indium tin oxide (ITO) film and highly reflective metal materials have been proposed. Compared with the conventional CBL structure which was inserted between ITO film and p-type GaN, simulation results showed that LEDs with a buried CBL in the ITO film effectively facilitated current spreading under the CBL. We demonstrated that buried CBL was beneficial for suppressing current crowding (CC) effect around the edge of CBL and may facilitate higher LED efficiency. Furthermore, experimental results showed that LEDs with the buried structure we proposed showed lower working voltage and higher light output power (LOP) compared with those with conventional CBL structure. These results further confirmed that the buried CBL scheme was effective to reduce current crowding (CC) effect. In addition, highly reflective metal materials of Cr/Al/Pt/Au were employed to reduce light absorption and achieve high light extraction efficiency. 相似文献
9.
Xianjie Shao Dawei Yan Hai Lu Dunjun Chen Rong Zhang Youdou Zheng 《Solid-state electronics》2011,57(1):9-13
The efficiency droop behavior of GaN-based light emitting diodes (LEDs) is studied when the LEDs are under reverse-current and high-temperature stress tests respectively. It is found that reverse-current stress mainly induces additional non-radiative recombination centers within the active region of InGaN/GaN multiple quantum wells, which degrade the overall efficiency of the GaN LED under test but push the peak-efficiency-current towards higher magnitude. The up-shift of peak-efficiency-current can be explained by a rate-equation model in which the newly-created defects by reverse-current stress enlarge the dominant low-current region of non-radiative recombinations. Comparatively, high-temperature stress mainly increases the series resistance of the LED under test. Although the overall efficiency of the GaN LED also drops, there is no shift of peak-efficiency-current induced by the high-temperature stress. 相似文献
10.
11.
12.
在这篇论文里,我们通过在InGaN/GaN 多量子阱和n型氮化镓层中间插入一层低温生长的n型氮化镓显著提高了LED的抗静电能力。通过引入低温生长的氮化镓插入层使得LED抗击穿电压超过4000V的良品率从9.9%提升到74.7%。低温生长的氮化镓插入层作为后续生长的多量子阱的缓冲层,释放了量子阱中的应力并且改善了量子阱的界面质量。另外,我们证明了在氮气气氛下生长低温氮化镓插入层对于LED抗静电能力的改善要强于氢气气氛,同时也进一步证明低温插入层对量子阱中应力的释放有利于提高LED的抗静电能力。光电测试结果表明,在引入低温nGaN缓冲层后,LED的电学特性并没有衰退,并且LED的光输出功率提高了13.9%。 相似文献
13.
R. J. Archer 《Journal of Electronic Materials》1972,1(1):127-153
III–V semiconductor display diodes fall into three material categories: direct, indirect, and diode-phosphor combinations.
The light generation mechanisms are well understood in each case. On the basis of the luminous efficacy achieved in the laboratory,
the merit of the various materials is in the order: GaP: N (green), GaP: Zn, O (red), GaInP (yellow), GaAsP (red), GaAlAs
(red) and GaAs-phosphor combinations (red, green, blue). A more comprehensive assessment of quality must take into account
factors such as the economic feasibility of the methods of synthesis, the applicability to monolithic arrays, and the suitability
of spectra (hue, contrast, saturation, etc.). The degree of importance of these matters and the limitations of the various
materials are less well-defined at present. New developments which may have an impact on the future of display diodes include
the use of AlxGa1-xP in place of GaP to shift spectra to shorter wavelengths, the possible development of very bright direct alloys of InP with
either GaP or A1P, and the doping of GaAsP with N to extend its range of colors. 相似文献
14.
High-brightness AlGaInP light emitting diodes 总被引:8,自引:0,他引:8
Vanderwater D.A. Tan I.-H. Hofler G.E. Defevere D.C. Kish F.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1997,85(11):1752-1764
First commercially introduced in 1990, AlGaInP light emitting diodes (LEDs) currently are the highest (luminous) efficiency visible solid-state emitters produced to date in the red through yellow spectral regime. The attainment of this high-efficiency performance is a result of the development of advanced metalorganic chemical vapor deposition crystal growth techniques, which have facilitated the high-quality growth of this quaternary alloy as well as the implementation of complex device designs. Furthermore, the highest efficiency family of AlGaInP devices (based upon a transparent-substrate platform and commercially introduced in 1994) have been realized as result of the development and implementation of direct compound semiconductor wafer bonding technology. As a result, the luminous efficiency of AlGaInP LEDs exceeds or rivals that of unfiltered incandescent lamps and other conventional lighting sources. Further improvements in these techniques (and the realization of efficient, high-power LEDs) are expected to make AlGaInP LEDs even more competitive with conventional lamp technology, thus enhancing the position of LED's in many applications as a preferred lighting source 相似文献
15.
The relationship between thickness of electron transport layer (ETL) and device performance of organic light-emitting diodes (OLEDs) was investigated. Especially, we prepared various OLEDs by varying the thickness of ETL to investigate the difference of device performance. Very interestingly, the device efficiency of green phosphorescent organic light emitting diodes (PHOLEDs) was significantly improved when the thickness of ETL was optimized even though we did not change any materials for such devices except that we applied highly conductive Li doped ETL. This means that the only one factor which is associated with an improvement of device efficiency could be originated from the constructive optical interference. As a result, the simple modification of PHOLEDs only by changing the optical thickness condition causes a dramatic improvement of current efficiency (up to 82.4 cd/A) as well as external quantum efficiency (EQE, up to 23.8%), respectively. Those values correspond to the much more improved ones (by ∼34.4%) compared to those obtained from the normal devices with thin ETL as a reference. 相似文献
16.
Cheng-Liang Wang Jyh-Rong Gong Ming-Fa Yeh Bor-Jen Wu Wei-Tsai Liao Tai-Yuan Lin Chung-Kwei Lin 《Photonics Technology Letters, IEEE》2006,18(14):1497-1499
We report the influence of short-period superlattice (SPSL)-inserted structures in the underlying undoped GaN on the characteristics of GaN-based light-emitting diodes (LEDs). The measurements of current-voltage (I-V) curves indicate that GaN-based LEDs having pseudomorphic Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL-inserted structures exhibit improvements in device characteristics with the best LED being inserted with two sets of five-pair Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL structure. Based upon the results of etch pit counts, double-crystal X-ray diffraction measurements and transmission electron microscopic observations of the GaN-based LEDs, it was found that the Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL-inserted structures tended to serve as threading dislocation filters in the LEDs so that the improved I-V characteristics were achieved. 相似文献
17.
An InGaN/GaN light-emitting diode (LED) combined with a metal–oxide semiconductor (MOS) capacitor has been fabricated for high electrostatic discharge (ESD) protection. By connecting a MOS capacitor in parallel with the GaN-based LED, a level of defense against the ESD is significantly strengthened from 200 to 1900 V of human body mode (HBM), which corresponds to 6- to 7-fold enhancement in the ESD robustness of LEDs. 相似文献
18.
用传输矩阵法模拟计算了AlGaInP发光二极管(LED)不同表面结构的光学特性,用等离子体增强化学气相沉积(PECVD)或磁控溅射掺铟氧化锡(ITO)设备,在带有DBR结构的外延衬底上制备出具有不同表面层结构的LED.通过实验结果对比表明,表面生长λ/4n SiON加λ2n ITO增透膜结构复合增透膜的LED,器件光学性能提高最佳,在20 mA注入电流下,光强和光通量分别达到141.7 mcd和0.4733 lm.比同样结构的无增透膜LED轴向光强和光通量分别提高138%和91%. 相似文献
19.
《Spectrum, IEEE》2003,40(6):26-29
Light-emitting diodes are ubiquitous in today's high-tech world. But no matter what their application or color, their origin can be traced to the red LED created in 1962 by Nick Holonyak Jr., the winner of this year's IEEE Medal of Honor. The article describes Holonyak's career and the work which produced the first LED, and shows how his influence permeates the industry today. 相似文献
20.
高亮度LED调光技术 总被引:1,自引:0,他引:1
高亮度发光二极管(HB LED)在各种领域应用普及.并要求HB LED具备有调光功能.在现有的几种调光技术中,从简单的可变电阻负载到复杂的脉冲宽度调制(PWM)开关,每一种方法均有其利弊.PWM调光的效率最高,电流控制也最精准.论述了HB LED在调光时的特性,介绍了LM3405评估板及其功能.包括其布局、原理图和元件清单. 相似文献