Luo Yi, Bai Yiming, Han Yanjun, Li Hongtao, Wang Lai, Wang Jian, Sun Changzheng, Hao Zhibiao, Xiong Bing
Opt Express. 2016 May 16;24(10):A797-809. doi: 10.1364/OE.24.00A797.
Indium tin oxide (ITO)/ indium oxide (InO) double layer structure was adopted as the transparent conduction and light scattering function layer to improve the light extraction efficiency of the GaN-based blue LEDs. The double layer structure was first deposited in one run by electron beam evaporation using ITO and Indium as the source respectively, and then annealed in an oxygen environment. This method can fabricate transparent electrode with microstructure and low specific contact resistivity one time free from lithography and etching, which makes the fabrication process simple and at a ower cost. For the 220 nm ITO/ 170 nm InO double layer sample annealed at 600°C for 15 min in oxygen, measurement results show that its root mean square of roughness of the surface microstructure can be as high as 85.2 nm which introduces the strongest light scattering. Its light transmittance at 450 nm can maintain 92.4%. At the same time, it can realize lower specific contact resistivity with p-InGaN. Compared with the GaN-based blue LEDs with only 220 nm ITO electrode, the light output power of the LEDs with 220 nm ITO/ 170 nm InO double layer structure can be increased about 58.8%, and working voltage at 20 mA injection current is decreased about 0.23 V due to the enhanced current spreading capability. The light output power improvement is also theoretically convinced by finite difference time domain simulations.
采用氧化铟锡（ITO）/氧化铟（InO）双层结构作为透明导电和光散射功能层，以提高氮化镓基蓝光发光二极管的光提取效率。该双层结构首先通过电子束蒸发分别以ITO和铟为源一次性沉积，然后在氧气环境中退火。这种方法可以一次性制备具有微观结构和低比接触电阻率的透明电极，无需光刻和蚀刻，使得制造工艺简单且成本较低。对于在氧气中600°C退火15分钟的220nm ITO/170nm InO双层样品，测量结果表明其表面微观结构的粗糙度均方根高达85.2nm，这引入了最强的光散射。其在450nm处的透光率可保持92.4%。同时，它与p-InGaN可以实现更低的比接触电阻率。与仅具有220nm ITO电极的氮化镓基蓝光发光二极管相比，具有220nm ITO/170nm InO双层结构的发光二极管的光输出功率可提高约58.8%，并且在20mA注入电流下的工作电压由于增强的电流扩展能力而降低约0.23V。有限时域差分模拟也从理论上证实了光输出功率的提高。
