共查询到20条相似文献,搜索用时 15 毫秒
1.
Enhanced performance of GaN-based light-emitting diodes with InGaN/GaN superlattice barriers
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
GaN-based multiple quantum well light-emitting diodes (LEDs) with conventional and superlattice barriers have been investigated numerically. Simulation results demonstrate using InGaN/GaN superlattices as barriers can effectively enhance performances of the GaN-Based LEDs, mainly owing to the improvement of hole injection and transport among the MQW active region. Meanwhile, the improved electron capture decreases the electron leakage and alleviates the efficiency droop. The weak polarization field induced by the superlattice structure strengthens the intensity of the emission spectrum and leads to a blue-shift relative to the conventional one. 相似文献
2.
Improved performance of near UV light-emitting diodes with a composition-graded p-AlGaN irregular sawtooth electron-blocking layer
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate the performances of the near-ultraviolet(about 350 nm-360 nm) light-emitting diodes(LEDs) each with specifically designed irregular sawtooth electron blocking layer(EBL) by using the APSYS simulation program.The internal quantum efficiencies(IQEs),light output powers,carrier concentrations in the quantum wells,energy-band diagrams,and electrostatic fields are analyzed carefully.The results indicate that the LEDs with composition-graded pAl_xGa_(1-x)N irregular sawtooth EBLs have better performances than their counterparts with stationary component p-AlGaN EBLs.The improvements can be attributed to the improved polarization field in EBL and active region as well as the alleviation of band bending in the EBL/p-AlGaN interface,which results in less electron leakage and better hole injection efficiency,thus reducing efficiency droop and enhancing the radiative recombination rate. 相似文献
3.
InGaN based light-emitting diodes (LEDs) with dip-shaped quantum wells and conventional rectangular quantum wells are numerically investigated by using the APSYS simulation software. It is found that the structure with dip-shaped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on numerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed mainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells (MQWs). 相似文献
4.
Improved performance of InGaN light-emitting diodes with a novel sawtooth-shaped electron blocking layer
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A sawtooth-shaped electron blocking layer is proposed to improve the performance of light-emitting diodes (LEDs). The energy band diagram, the electrostatic field in the quantum well, the carrier concentration, the electron leakage, and the internal quantum efficiency are systematically studied. The simulation results show that the LED with a sawtooth-shaped electron blocking layer possesses higher output power and a smaller efficiency droop than the LED with a conventional A1GaN electron blocking layer, which is because the electron confinement is enhanced and the hole injection efficiency is improved by the appropriately modified electron blocking layer energy band. 相似文献
5.
Jian-Yong Xiong Yi-Qin Xu Bin-Bin Ding Fang Zhao Jing-Jing Song Shu-Wen Zheng Li Zhang Tao Zhang Guang-Han Fan 《Applied Physics A: Materials Science & Processing》2013,113(2):315-319
The blue InGaN light-emitting diodes (LEDs), employing a lattice-compensated p-AlGaN/InGaN superlattice (SL) interlayer to link the last quantum barrier and electron blocking layer (EBL), are proposed and investigated numerically. The simulation results indicate that the newly designed LEDs have better hole injection efficiency, lower electron leakage, and smaller electrostatic fields in the active region over the conventional LEDs mainly attributed to the mitigated polarization-induced downward band bending. Furthermore, the markedly improved output power and efficiency droop are also suggested when the conventional LEDs corresponding to experiment data are replaced by the newly designed LEDs. 相似文献
6.
Droop improvement in blue InGaN light-emitting diodes with GaN/InGaN superlattice barriers
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
GaN/InGaN superlattice barriers are used in InGaN-based light-emitting diodes (LEDs). The electrostatic field in the quantum wells, electron hole wavefunction overlap, carrier concentration, spontaneous emission spectrum, light-current performance curve, and internal quantum efficiency are numerically investigated using the APSYS simulation software. It is found that the structure with GaN/InGaN superlattice barriers shows improved light output power, and lower current leakage and efficiency droop. According to our numerical simulation and analysis, these improvements in the electrical and optical characteristics are mainly attributed to the alleviation of the electrostatic field in the active region. 相似文献
7.
Miao-Chan Tsai Sheng-Horng Yen Yen-Kuang Kuo 《Applied Physics A: Materials Science & Processing》2011,104(2):621-626
The concept of a step-like quantum well is proposed with the purpose to reduce the influence of electrostatic field resulting
from the piezoelectric effect on the optical performance of blue InGaN light-emitting diodes. Particularly, the optical properties
of the LED structures with the In0.23Ga0.77N single quantum well, In0.20Ga0.80N/In0.26Ga0.74N step-like quantum well, and In0.26Ga0.74N/In0.20Ga0.80N step-like quantum well are numerically investigated in detail. Simulation results show that the In0.20Ga0.80N/In0.26Ga0.74N step-like-quantum-well LED structure has the best optical performance in virtue of the improvement in spatial overlap of
electrons and holes in the quantum well. 相似文献
8.
Z. Gong Y. F. Zhang P. Kelm I. M. Watson E. Gu M. D. Dawson 《Applied Physics A: Materials Science & Processing》2011,103(2):389-393
We present the fabrication details and performance characteristics of InGaN light-emitting diodes (LEDs) consisting of arrays
of interconnected micro-pixels where each micro-pixel is nano-textured via nano-imprinting. We have taken the further step
of embodying the pixels in a rhomboidal geometry. It is found that the power output of these nano-textured micro-LEDs with
rhomboidal geometries is 57% higher than that of conventional square-shaped broad-area reference LEDs. The series resistance
of the textured LEDs is reduced, owing to the multi-finger electrodes introduced. Furthermore, these LEDs can sustain higher
operation current of up to 500 mA without encapsulation, suggesting improved thermal dissipation capability. Finally, the
combined effects of surface texturing, micro-LED configuration, and geometric shaping on the light extraction are analyzed.
It is found that the power enhancement by surface texturing, micro-pixellating and the rhomboidal geometry are 32%, 16%, and
9%, respectively, implying that surface texturing is the most effective contribution to increasing the light extraction efficiency
in our design. The angular dependent far-field beam profile is also remarkably changed, compared with the standard Lambertian
emission pattern of the conventional square-shaped LEDs. Substantial increase in the EL intensity is evident from both the
top surface and the sidewall. 相似文献
9.
Yang Sheng Chang Sheng Xia Zhan Ming Simon Li Li Wen Cheng 《Optical and Quantum Electronics》2013,45(7):605-610
Blue InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) with patterned sapphire substrate (PSS) are simulated by the APSYS software. Approach of combining finite-difference time-domain (FDTD) method and raytracing technique is applied to perform light extraction. The simulation results show that PSS dramatically increases extraction efficiency of light power, in agreement with experiment. It is found that extraction efficiency can be maximized by changing the shape of PSS. This work presents a new approach to combine electrical simulation with FDTD and raytracing in 3D TCAD simulation of GaN-LED. 相似文献
10.
J.-R. Chen Y.-C. Wu S.-C. Ling T.-S. Ko T.-C. Lu H.-C. Kuo Y.-K. Kuo S.-C. Wang 《Applied physics. B, Lasers and optics》2010,98(4):779-789
The physical mechanisms leading to the efficiency droop of InGaN/GaN light-emitting diodes (LEDs) are theoretically investigated.
We first discuss the effect of Auger recombination loss on efficiency droop by taking different Auger coefficients into account.
It is found that the Auger recombination process plays a significant nonradiative part for carriers at typical LED operation
currents when the Auger coefficient is on the order of 10−30 cm6 s−1. Furthermore, the InGaN/GaN multiple-quantum-well (MQW) LEDs with varied indium compositions in InGaN quantum wells are studied
to analyze the wavelength-dependent efficiency droop. The simulation results show that the wavelength-dependent efficiency
droop is caused by several different effects including non-uniform carrier distribution, electron overflow, built-in electrostatic
field induced by spontaneous and piezoelectric polarization, and Auger recombination loss. These internal physical mechanisms
are the critical factors resulting in the wavelength-dependent efficiency droop in InGaN/GaN MQW LEDs. 相似文献
11.
12.
A potential application of blue-light-emitting InGaN LED's as a polymerizing source for dental composite materials is described. We compared a basic LED device with a conventional curing light in vitro to determine the polymerization parameters and to examine the effect of the curing process on the physical properties of these materials. It was determined that an array of six LED's was able to set a range of composite materials more quickly than a conventional light source, with the cured compounds showing similar hardness and material shrinkage parameters but with a lower material temperature rise during the curing process using the array. These findings indicate that a device consisting of several InGaN LED's would be an effective instrument for curing certain light-sensitive materials, particularly dental composites. 相似文献
13.
The effect of using chirped multiple quantum-well (MQW) structures in InGaN green light-emitting diodes (LEDs) is numerically investigated. An active structure, which is with both thick QWs with low indium composition on the p-side and thin QWs with high indium composition next to the n-region, is presented in this study. The thickness and indium composition in each single QW is specifically tuned to emit the same green emission spectrum. Comparing with conventional active structure design of green LEDs, which is using uniform MQWs, the output power is increased by 27% at 20 mA, and by 15% at 100 mA current injections. This improvement is mainly attributed to the enhanced efficiency of carrier injection into QWs and the improved capability of carrier transport. 相似文献
14.
15.
We employed the APSYS software to perform 3D electrical and ray-tracing simulations on micro-ring light-emitting diodes (LEDs)
to verify previous experimental findings that they have higher extraction efficiency than micro-disk and broad area LEDs.
3D ray-tracing indicates the importance of inter-ring optical interactions. Furthermore we found that the higher light extraction
efficiency is at the expense of reduced internal quantum efficiency (IQE) as injection current is increased. 相似文献
16.
The advantages of blue InGaN light-emitting diodes with low bandgap energy and polarization-matched AlGaInN barriers are demonstrated numerically. Simulation results show that, besides the common benefit of enhanced electron-hole spatial overlap in the quantum well from the polarization-matched condition, the lower bandgap energy barriers can have additional advantages of more uniform carrier distribution among quantum wells while maintaining sufficient electron confinement. The internal quantum efficiencies of all the polarization-matched structures under study exhibit less severe efficiency droop, which is presumably attributed to the suppression of Auger recombination. 相似文献
17.
Kang JH Kim HG Chandramohan S Kim HK Kim HY Ryu JH Park YJ Beak YS Lee JS Park JS Lysak VV Hong CH 《Optics letters》2012,37(1):88-90
The effect of triangular air prism (TAP) arrays with different distance-to-width (d/w) ratios on the enhancement of light extraction efficiency (LEE) of InGaN light-emitting diodes (LEDs) is investigated. The TAP arrays embedded at the sapphire/GaN interface act as light reflectors and refractors, and thereby improve the light output power due to the redirection of light into escape cones on both the front and back sides of the LED. Enhancement in radiometric power as high as 117% and far-field angle as low as 129° are realized with a compact arrangement of TAP arrays compared with that of a conventional LED made without TAP arrays under an injection current of 20 mA. 相似文献
18.
High-power and high-reliability GaN/InGaN flip-chip light-emitting
diodes (FCLEDs) have been demonstrated by employing a flip-chip
design, and its fabrication process is developed. FCLED is composed
of a LED die and a submount which is integrated with circuits to
protect the LED from electrostatic discharge (ESD) damage. The LED
die is flip-chip soldered to the submount, and light is extracted
through the transparent sapphire substrate instead of an absorbing
Ni/Au contact layer as in conventional GaN/InGaN LED epitaxial
designs. The optical and electrical characteristics of the FCLED are
presented. According to ESD IEC61000-4-2 standard (human body
model), the FCLEDs tolerated at least 10\,kV ESD shock have ten
times more capacity than conventional GaN/InGaN LEDs. It is shown
that the light output from the FCLEDs at forward current 350mA with
a forward voltage of 3.3\,V is 144.68\,mW, and 236.59\,mW at 1.0\,A
of forward current. With employing an optimized contact scheme the
FCLEDs can easily operate up to 1.0\,A without significant power
degradation or failure. The life test of FCLEDs is performed at
forward current of 200\,mA at room temperature. The degradation of
the light output power is no more than 9\% after 1010.75\,h of life
test, indicating the excellent reliability. FCLEDs can be used in
practice where high power and high reliability are necessary, and
allow designs with a reduced number of LEDs. 相似文献
19.
Performance improvement of InGaN blue light-emitting diodes with several kinds of electron-blocking layers
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The performance of InGaN blue light-emitting diodes(LEDs) with different kinds of electron-blocking layers is investigated numerically.We compare the simulated emission spectra,electron and hole concentrations,energy band diagrams,electrostatic fields,and internal quantum efficiencies of the LEDs.The LED using AlGaN with gradually increasing Al content from 0% to 20% as the electron-blocking layer(EBL) has a strong spectrum intensity,mitigates efficiency droop,and possesses higher output power compared with the LEDs with the other three types of EBLs.These advantages could be because of the lower electron leakage current and more effective hole injection.The optical performance of the specifically designed LED is also improved in the case of large injection current. 相似文献
20.
利用金属有机物化学气相沉积系统在蓝宝石衬底上通过有源层的变温生长,得到In组分渐变的量子阱结构,从而获得具有三角形能带结构的InGaN/GaN多量子阱发光二极管(LED)(简称三角形量子阱结构LED).变温光致发光谱结果表明,相对于传统具有方形能带结构的量子阱LED(简称方形量子阱结构LED),三角形量子阱结构有效提高了量子阱中电子和空穴波函数的空间交叠,从而增加了LED的内量子效率;电致发光谱结果表明,三角形量子阱结构LED器件与传统结构LED器件相比,明显改善了发光峰值波长随着电流的蓝移现象.通过以上 相似文献