ZnO∶Al替代ITO作透明导电膜的应用

研究了AZO(ZnO∶Al)替代ITO透明导电膜在GaN基LED中的应用,通过脉冲激光沉积和磁控溅射法制作了AZO薄膜,分析了AZO与p型GaN不良的欧姆接触的物理机理,并利用插入ITO薄层来改善接触电阻,实验用ITO 20nm/AZO 500nm的复合导电薄膜做透明导电薄膜,成功得到了波长为525.74nm、亮度为380.88mcd、电压为3.35V的GaN基绿光LED芯片,相当于单一ITO透明导电膜的性能,整个试验工艺中减少了ITO的使用量,降低了LED芯片的制造成本。     

快速热退火对ITO薄膜及LED芯片性能的影响

采用金属有机化学气相沉积(MOCVD)技术在蓝宝石衬底上制备了GaN基LED外延层,采用磁控溅射法制备了氧化铟锡(ITO)薄膜,ITO薄膜用于制作与p-GaN的欧姆接触.研究了快速热退火温度为550℃,退火时间为200 s时,不同氧气体积流量对ITO薄膜性能及LED芯片光电性能的影响.结果表明:不通氧气时,ITO薄膜的方块电阻和透过率分别为33 Ω/口和93.1％,LED芯片出现电流拥挤效应,其电光转换效率只有33.3％;氧气体积流量为1 cm3/min时,ITO薄膜的方块电阻和透过率分别为70 Ω/口和95.9％,LED芯片的电流扩展不佳,其正向电压较高,电光转换效率为43.8％;氧气体积流量为0.4 cm3/min时,ITO薄膜的方块电阻和透过率分别为58 Ω/口和95.4％,LED芯片的电流扩展最佳,其亮度最高、正向电压最低,电光转换效率较高,为52.9％.     

透明导电ITO欧姆接触的AlGaInP薄膜发光二极管

提出了一种透明导电氧化铟锡(ITO)欧姆接触的AlGaInP薄膜发光二极管(LED)的结构和制作工艺.在这个结构里,ITO还作为窗口层材料,增强电流扩展,并应用了高反射率的金属作为反光镜.用Au-Sn合金(Au∶Sn＝8∶2,重量比)作为焊料,把带有金属反光镜的AlGaInP LED(RS-LED)外延片倒装键合到GaAs基板上,并去掉外延GaAs衬底,把被GaAs衬底吸收的光反射出去.与常规AlGaInP吸收衬底LEDs(AS-LED)和带有分布布拉格反光镜(DBR)的AlGaInP吸收衬底LEDs(DBR-AS-LED)电、光特性的比较,用透明导电ITO做欧姆接触的AlGaInP薄膜RS-LED结构能极大提高光输出功率和发光强度.正向电流20 mA时,RS-LED的光输出功率分别是AS-LED和DBR-AS-LED的2.4倍和1.7倍;RS-LED 20 mA下峰值波长624 nm的轴向光强达到了179.6 mcd,分别是AS-LED 20 mA下峰值波长627 nm和DBR-AS-LED 20 mA下峰值波长623 nm轴向光强的2.2倍和1.3倍.     

ICP刻蚀p-GaN表面微结构GaN基蓝光LED

采用基于Cl2/Ar/BCl3气体的感应耦合等离子体(ICP)刻蚀技术制作了p-GaN表面具有直径3 μm、周期6 μm的二维圆孔微结构GaN基蓝光LED,研究了刻蚀深度对光荧光(PL)和发光二极管(LED)光电特性的影响.结果表明,刻蚀深度为25 nm的表面微结构,与传统平面结构相比,其PL增强了42.8%;而采用ITO作为透明电极的LED,在20 mA注入电流下,正面出光增强了38%、背面出光增强了10.6%,同时前向电压降低了0.6 V,反向漏电流基本不变.     

基于ITO键合技术的白光发光二极管特性研究

根据色度学原理计算,通过选择匹配的基色波长和功率,制备了GaN/GaAs基ITO键合白光发光二极管(LED),得到了等能白光。通过测试发现,在20mA下,电压为5.3V,此方法是制备固态照明用白光LED的有效方法之一。     

具有ITO/Ti3O5薄膜结构的高亮度AlGaInP LED

采用ITO/Ti_3O_5薄膜结构作为高亮度AlGaInP LED的电流扩展层、窗口层、电流阻挡层和增透膜层。通过在电极下形成肖特基结,避免电极下方无效电流注入,提高局域电流密度。通过ITO/Ti_3O_5增透膜设计提升LED的光提取效率。具有该ITO/Ti_3O_5薄膜结构的主波长621 nm的高亮度AlGaInP LED芯片(150μm×150μm)较传统结构芯片发光强度提升40%,20 mA注入电流下,电压均值在2.1 V左右。     

Ni纳米粒子掩膜用于提高GaN基LED出光率的研究

以无水乙醇为溶剂、柠檬酸为分散剂,用超声分散技术配制Ni纳米粒子分散液;将分散液用旋涂的方法在GaN基发光二极管(LED)的ITO电流扩展层上制备单层Ni纳米粒子掩膜,采用ICP(inductively coupledplasma)干法刻蚀技术在ITO层上制作出表面粗化的结构。在20 mA工作电流下,与普通GaN基LED相比,这种ITO表面粗化的GaN基LED芯片发光强度提高了30%,并且对器件的电性能影响很小。结果表明,该表面粗化技术是一种工艺简单、成本低和能有效提高LED发光效率的方法。     

一定可视角的超高亮度蓝光LED

报道了封装大芯片InGaN/GaN蓝光发光二极管(LED)的实验结果.在室温下,正向电压为3.3V和电流为350mA时,其轴向亮度为16×104cd/m2,可视角为98°.     

非平面化型ITO氮化镓基蓝光发光二极管

将氧化铟锡(ITO)生长于氮化镓基蓝色发光二极管的出光台面上(p型GaN台面),用非平面化处理的方法制作出ITO井状结构,研制出非平面化型氧化铟锡-氮化镓基蓝色发光二极管(LED),获得了高的出光效率.结果表明,在20mA工作电流下,该蓝色发光二极管的出光光强是平整的普通ITO-GaN基LED的1.35倍.     

高功率GaN p—n结蓝色发光二极管

用具有 GaN 缓冲层的 GaN 薄膜制备出高功率 p—n 结蓝色发光二极管(LEDs)。外部量子效率高达0.18%,输出功率比常规的亮度为8mcd 的 SiC 蓝色 LEDs 高出10倍。在正向电流为20mA 的条件下,正向电压低至4V;这是报导过的 GaNLEDs 中最低的正向电压值。峰值波长和半最大值全宽度(FWHM)分别为430nm 和55nm。     

Enhanced output power of (indium) gallium nitride light emitting diodes by a transparent current spreading-film composed of a disordered network of indium tin oxide nanorods

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.     

Enhanced output power of InGaN-GaN light-emitting diodes with high-transparency nickel-oxide-indium-tin-oxide Ohmic contacts

This study develops a highly transparent nickel-oxide (NiO/sub x/)-indium-tin-oxide (ITO) transparent Ohmic contact with excellent current spreading for p-GaN to increase the optical output power of nitride-based light-emitting diodes (LEDs). The NiO/sub x/-ITO transparent Ohmic contact layer was prepared by electron beam in-situ evaporation without postdeposition annealing. Notably, the transmittance of the NiO/sub x/-ITO exceeds 90% throughout the visible region of the spectrum and approaches 98% at 470 nm. Moreover, GaN LED chips with dimensions of 300 /spl times/ 300 /spl mu/m fabricated with the NiO/sub x/-ITO transparent Ohmic contact were developed and produced a low forward voltage of 3.4 V under a nominal forward current of 20 mA and a high optical output power of 6.6 mW. The experimental results indicate that NiO/sub x/-ITO bilayer Ohmic contact with excellent current spreading and high transparency is suitable for fabricating high-brightness GaN-based light-emitting devices.     

Nitride-based flip-chip ITO LEDs

Nitride-based flip-chip indium-tin-oxide (ITO) light-emitting diodes (LEDs) were successfully fabricated. It was found that the forward voltage and the 20 mA output power of the flip-chip ITO LED were 3.32 V and 14.5 mW, respectively. Although the operation voltage of such a flip-chip ITO LED was slightly larger, it was found that its output power was much larger than those of conventional nonflip-chip LEDs. It was also found that flip-chip ITO LEDs were more reliable.     

在侧壁形成导热膜的GaN基发光二极管

研制了一种在侧壁形成导热膜的GaN基发光二极管(LED),其中导热层由氮氧化铝形成,导热层外再覆盖一保护层,保护层选自氧化物、氮化物或氟化物.对LED进行电流加速老化实验,分析输出功率随老化时间的变化关系,可以看到侧壁形成导热膜的GaN基LED的输出功率衰减缓慢.实验表明由于氮氧化铝膜具有良好的导热性,其可以有效地耗散发光部分产生的热量,因此在器件侧壁形成AlON导热膜可以改善GaN基LED的输出特性并提高器件的可靠性.     

High-Efficiency GaN-Based Light-Emitting Diodes Fabricated With Metallic Hybrid Reflectors

We report on high-efficiency GaN-based light-emitting diodes (LEDs) fabricated with metallic hybrid reflectors (MHRs). It is shown that the MHRs consisting of an injection part (with low p-contact resistance and intermediate reflectance) and a spreading part (with high p-contact resistance and good reflectance) can enhance current injection and overall light reflectivity. Compared with reference LEDs with single reflectors, LEDs fabricated with Ag-based MHRs give higher output power by 8.9% and a reduction in forward voltage by 0.02 V (at 20 mA), resulting in the improvement of the power efficiency by 10%.     

用表面粗化ITO的欧姆接触提高GaN基LED性能

应用ICP干法刻蚀工艺和自然光刻技术,制备了ITO表面粗化的GaN基LED芯片。聚苯乙烯纳米颗粒在干法刻蚀中作为刻蚀掩膜。通过扫描电镜(SEM)观察ITO薄膜的粗糙度,并且报道了优化的粗化工艺参数。结果表明,ITO表面粗化的GaN基LED芯片同传统的表面光滑的芯片相比在20 mA的驱动电流下,发光强度提高了70%。     

ICP dry etching ITO to improve the performance of GaN-based LEDs

In order to improve the light efficiency of the conventional GaN-based light-emitting diodes(LEDs), the indium tin oxide(ITO) film is introduced as the current spreading layer and the light anti-reflecting layer on the p-GaN surface.There is a big problem with the ITO thin film’s corrosion during the electrode preparation.In this paper,at least,the edge of the ITO film was lateral corroded 3.5μm width,i.e.6.43%—1/3 of ITO film’s area. An optimized simple process,i.e.inductively couple plasma(ICP),was introduced to solve this problem.The ICP process not only prevented the ITO film from lateral corrosion,but also improved the LED’s light intensity and device performance.The edge of the ITO film by ICP dry etching is steep,and the areas of ITO film are whole. Compared with the chip by wet etching,the areas of light emission increase by 6.43%at least and the chip’s lop values increase by 45.9%at most.     

Highly reliable GaN-based light-emitting diodes formed by p-In/sub 0.1/Ga/sub 0.9/N-ITO structure

Indium-tin-oxide (ITO) is deposited as a transparent current spreading layer of GaN-based light-emitting diodes (LEDs). To reduce the interfacial Schottky barrier height, a thin p-In/sub 0.1/Ga/sub 0.9/N layer is grown as an intermediate between ITO and p-GaN. The contact resistivity around 2.6/spl times/10/sup -2/ /spl Omega//spl middot/cm/sup 2/ results in a moderately high forward voltage LED of 3.43 V operated at 20 mA. However, the external quantum efficiency and power efficiency are enhanced by 46% and 36%, respectively, in comparison with the conventional Ni-Au contact LEDs. In the life test, the power degradation of the p-In/sub 0.1/Ga/sub 0.9/N-ITO contact samples also exhibits a lower value than that of the conventional ones.     

Improved light extraction efficiency of GaN-based light emitting diodes using one and two interfaces of ITO/ZnO layer texturing

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.