共查询到20条相似文献,搜索用时 31 毫秒
1.
Yan Shen Huayong Xu Xiangang Xu Qing Liu Huan Liu Kai Jiang Xiaobo Hu 《Materials Science in Semiconductor Processing》2013,16(6):1719-1722
A thin film consisting of a disordered nanorod network of indium tin oxide (ITO) and conventional ITO films are fabricated on gallium nitride (GaN) based-light emitting diodes (LEDs) by electron beam evaporation. The surface morphologies are observed by scanning electron microscopy (SEM). The disordered nanorod network of ITO is grown in vacuum without oxygen. It can be applied directly on the LED as the current spreading film unlike other nanorods which require growth on a conductive layer. The transmittance, current–voltage characteristic, and the dependence of light output power on current are measured for disordered nanorod network ITO LEDs and conventional ITO LEDs, respectively. The measurement results indicate that the nanorod network provides a significant improvement in the light output power of GaN-based LEDs. The influence of the structure of ITO films on the light output power of GaN-based LEDs is discussed. 相似文献
2.
Enhanced light output in nitride-based light-emitting diodes by roughening the mesa sidewall 总被引:1,自引:0,他引:1
Chia-Feng Lin Zhong-Jie Yang Jing-Hui Zheng Jing-Jie Dai 《Photonics Technology Letters, IEEE》2005,17(10):2038-2040
In this letter, we will report on a nitride-based light emitting diode with a mesa sidewall roughening process that increases light output power. The fabricated GaN-based light-emitting diode (LED) wafers were first treated through a photoelectrochemical (PEC) process. The Ga/sub 2/O/sub 3/ layers then formed around the GaN : Si n-type mesa sidewalls and the bottoms mesa etching regions. Selective wet oxidation occurred at the mesa sidewall between the p- and the n-type GaN interface. The light output power of the PEC treated LED was seen to increase by about 82% which was caused by a reduced index reflectance of GaN-Ga/sub 2/O/sub 3/-air layers, by a rough Ga/sub 2/O/sub 3/ surface, by a microroughening of the GaN sidewall surface, and by a selective oxidation step profile of the mesa sidewall that increases the light-extraction efficiency from the mesa sidewall direction. Consequently, this wet PEC treated process is suitable for high powered nitride-based LEDs lighting applications. 相似文献
3.
Hsu S.-C. Lee C.-Y. Hwang J.-M. Su J.-Y. Wuu D.-S. Horng R.-H. 《Photonics Technology Letters, IEEE》2006,18(23):2472-2474
We have demonstrated enhanced output power from roughened GaN-based light-emitting diodes (LEDs) by using electrodeless photoelectrochemical etching with a chopped source (ELPEC-CS etching). It was found that the 20-mA output power of the ELPEC-CS treated LED (with roughened surfaces on the top p-type and bottom n-type GaN surface as well as the mesa sidewall) was 1.41 and 2.57 times as high as those LEDs with a roughened p-type GaN surface and a conventional surface, respectively. The light output pattern of the ELPEC-CS treated LED was five times greater than the conventional LED at 0deg which was caused by the roughened GaN surface that improved the light extraction efficiency of the LED 相似文献
4.
5.
We report the enhancement of light extraction efficiency (LEE) and electrical performance in GaN-based green light-emitting diodes (LEDs) using ZnO nanorods formed on the etched surface of p-GaN. Green LEDs with hybrid ZnO nanorod structures grown on the hexagonally etched topmost layer of the LEDs, show an improvement in electroluminescence intensity that is 3.5 times higher than LEDs without any other surface treatments. The improvement in LEE in LEDs with nanohybrid structures was confirmed by finite-difference time-domain simulation analysis. Besides LEE enhancement, the surface etching effects on the reduction of leakage current of fabricated LEDs were also investigated. 相似文献
6.
纳米柱GaN基多量子阱(MQW)拥有量子尺寸效应以及应变释放等特性,对于提高GaN基发光二极管(LED)的发光效率具有重要意义.采用快速热退火(RTA)形成的自组装Ni纳米颗粒作为刻蚀掩膜,利用电感耦合等离子体反应离子刻蚀(ICP-RIE)制备纳米柱InGaN/GaN MQW.通过改变RTA温度发现在800℃以上才能有效形成Ni纳米颗粒掩膜.不同的ICP和射频(RF)功率条件下制备的纳米柱MQW光致发光强度相比于相同结构的平面MQW会发生显著变化.通过优化ICP-RIE的刻蚀条件,可以获得发光强度显著提高的纳米柱MQW结构.同时,纳米柱MQW中压电极化场的减弱会形成光致发光峰位蓝移. 相似文献
7.
Improvement of InGaN-GaN light-emitting diode performance with a nano-roughened p-GaN surface 总被引:2,自引:0,他引:2
Hung-Wen Huang C.C. Kao J.T. Chu H.C. Kuo S.C. Wang C.C. Yu 《Photonics Technology Letters, IEEE》2005,17(5):983-985
This investigation describes the development of InGaN-GaN light-emitting diode (LED) with a nano-roughened top p-GaN surface which uses Ni nano-mask and wet etching. The light output of the InGaN-GaN LED with a nano-roughened top p-GaN surface is 1.4 times that of a conventional LED, and wall-plug efficiency is 45% higher. The operating voltage of InGaN-GaN LED was reduced from 3.65 to 3.5 V at 20 mA and the series resistance was reduced by 20%. The light output is increased by the nano-roughening of the top p-GaN surface. The reduction in the series resistance can be attributed to the increase in the contact area of nano-roughened surface. 相似文献
8.
Wei-Chih Lai Chen P.H. Chang L.C. Cheng-Huang Kuo Jinn-Kong Sheu Tun C.J. Shei S.C. 《Photonics Technology Letters, IEEE》2009,21(18):1293-1295
In this letter, the authors report the fabrication of GaN-based light-emitting diodes (LEDs) with mesh indium-tin-oxide p-contact and nanopillars on patterned sapphire substrate. Using hydrothermal ZnO nanorods as the etching hard mask, the authors successfully formed vertical GaN nanopillars inside the mesh regions and on the mesa-etched regions. It was found that 20-mA forward voltage and reverse leakage currents observed from the proposed LED were only slightly larger than those observed from the conventional LEDs. It was also found that output power of the proposed LED was more than 80% larger than that observed from conventional LED prepared on flat sapphire substrate. 相似文献
9.
Yea-Chen Lee Chia-En Lee Hao-Chung Kuo Tien-Chang Lu Shing-Chung Wang 《Photonics Technology Letters, IEEE》2008,20(5):369-371
AlGaInP-based light-emitting diodes (LEDs) with a transparent sapphire substrate were fabricated by the glue-bonding (GB) method. This transparent sapphire substrate is a geometric shaping structure by wet etching processes. Furthermore, the n-side-up surface has a nano-roughened texture by natural mask and chemical wet etching processes. The light output of this novel LED structure could be enhanced about 26.7% (at 350 mA) due to the higher light extraction as compared with the conventional GB-LEDs. 相似文献
10.
Chung-Chieh Yang Chia-Feng Lin Jen-Hao Chiang Hsun-Chih Liu Chun-Min Lin Feng-Hsu Fan Chung-Ying Chang 《Journal of Electronic Materials》2009,38(1):145-152
InGaN-based light-emitting diodes (LEDs) were fabricated to have a higher light extraction through the photoelectrochemical
(PEC) mesa shaping process. After the PEC selective wet oxidation and wet etching processes, stable and controllable crystallographic
etching planes were formed as p-type GaN {} planes and n-type GaN {} planes included at an angle of 27 deg. The ever-present cone-shaped structure of a PEC-treated LED has a larger light scattering
area and higher light extraction cones on the mesa sidewall, as analyzed by microphotoluminescence and light output power
measurement. This cone-shaped-sidewall LED has a higher light output power and a larger divergence angle compared with a conventional
LED measured in an LED chip form. 相似文献
11.
Haiyong Gao Fawang Yan Yang Zhang Jinmin Li Yiping Zeng Guohong Wang 《Solid-state electronics》2008,52(6):962-967
Sapphire substrates patterned by a selective chemical wet and an inductively coupled plasma (ICP) etching technique was proposed to improve the performance of GaN-based light-emitting diodes (LEDs). GaN-based LEDs were fabricated on sapphire substrates through metal organic chemical vapor deposition (MOCVD). The LEDs fabricated on the patterned substrates exhibit improved device performance compared with the conventional LED fabricated on planar substrates when growth and device fabricating conditions were the same. The light output powers of the LEDs fabricated on wet-patterned and ICP-patterned substrates were about 37% and 17% higher than that of LEDs on planar substrates at an injection current of 20 mA, respectively. The enhancement is attributable to the combination of the improvement of GaN-based epilayers quality and the improvement of the light extraction efficiency. 相似文献
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13.
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
14.
High light-extraction (external quantum efficiency ~40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double diffuse surfaces were fabricated. This novel LED structure includes one top transmitted diffuse surface and another diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 degC. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted diffuse surfaces with hexagonal-cone morphology. The double diffused surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side diffused surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10 -8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double diffused surfaces could be responsible for the enhancement in the device light output power 相似文献
15.
Wei S.C. Su Y.K. Chang S.J. Shi-Ming Chen Wen-Liang Li 《Electron Devices, IEEE Transactions on》2005,52(6):1104-1109
Nitride-based light emitting diodes (LEDs) separately prepared with a conventional single low-temperature (LT) GaN nucleation layer and multiple GaN-SiN nucleation layers were both prepared. It was found that we could reduce defect density and thus improve crystal quality of the GaN-based LEDs by using multiple GaN-SiN nucleation layers. With a 20-V applied reverse bias, it was found that the reverse leakage currents measured from the LED with a single LT GaN nucleation layer and the one with 10-pair GaN-SiN nucleation layers were 1.5/spl times/10/sup -4/ and 2.5/spl times/10/sup -6/ A, respectively. It was also determined that we could use the multiple GaN-SiN nucleation layers to enhance the output intensity of near ultraviolet (UV) LEDs and to improve the reliability of nitride-based LEDs. 相似文献
16.
Kao C.-C. Kuo H. C. Yeh K. F. Chu J. T. Peng W. L. Huang H. W. Lu T. C. Wang S. C. 《Photonics Technology Letters, IEEE》2007,19(11):849-851
In this paper, we report the fabrication and characteristics of nano-roughened GaN laser lift-off (LLO) light-emitting diodes (LEDs) with different scale surface roughness. The surface roughness of devices was controlled by inductively coupled plasma reactive ion etching. Using this fabrication method to form nano-scaled roughness, the electrical property was almost not degraded. Furthermore, the light-output power and wall-plug efficiency of LLO LED could be both significantly enhanced about two times using this simple method 相似文献
17.
GaN-based nanoporous green LEDs with different pore depth have been fabricated by using anodic aluminum oxide (AAO) as dry etching mask. The experimental results show that the electrical properties of the nanoporous LEDs with different pore depths are similar, but for the optical properties, the LEDs with nanopores extended to the p-GaN layer exhibits the best performance, if increase the depth to MQWs or decrease to the ITO layer will both decrease the light output power (LOP). By calculating the light extraction efficiency using three-dimensional (3D) finite-difference time-domain method, the decrease of the light output is mainly attributed to the reduced light extraction efficiency when the pore depth stop at ITO transparent layer instead of p-type layer, while if the depth reach the MQWs, the deterioration of the QWs which is caused by dry etching damage will play an important role. This optimization would give a valuable guidance to the surface structure design for nanostructured GaN-based LEDs, such as surface roughening, photonic crystal, or top-down fabricated surface-plasmon enhanced LEDs. 相似文献
18.
《Electron Device Letters, IEEE》2009,30(5):496-498
19.
Y.J. Lee J.M. Hwang T.C. Hsu M.H. Hsieh M.J. Jou B.J. Lee T.C. Lu H.C. Kuo S.C. Wang 《Photonics Technology Letters, IEEE》2006,18(10):1152-1154
GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57/spl deg/ against {0001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme. 相似文献
20.
The material and electrical properties of GaN-based light-emitting diodes (LEDs) grown on wet-etched stripe-patterned substrates
were investigated. Footprint-like patterns, located directly above the inclined groove sidewalls, were found on the as-grown
LED surface. Cross-sectional transmission electron microscopy (TEM) showed that ‘tumor’-like structures with poor crystal
quality were initiated on the inclined sidewalls, seeding dislocation bundles in the subsequently grown crystal. The high
dislocation density slowed down the growth above the inclined sidewall, resulting in the uneven morphology. The fabricated
devices showed over 30% enhancement in light output power as a result of improvements in both internal and extraction efficiencies. 相似文献