ITO表面粗化提高GaN基LED芯片出光效率

使用现有生产线上工艺成熟且成本低廉的技术实现ITO粗化以提高GaN基LED蓝光芯片的出光效率是产业界重要的研究课题。本文通过普通光刻技术和湿法腐蚀技术，实现ITO表面粗化，有效地提高了LED芯片的输出光功率。输入电流为20 mA时，ITO层制备密集分布的三角周期圆孔阵列后，芯片输出光功率提升11.4%，但正向电压升高0.178 V；微结构优化设计后，芯片输出光功率提升8.2%，正向电压仅升高0.044 V。小电流注入时，密集分布的三角周期圆孔阵列有利于获得较高的输出光功率。大电流注入时，这种结构将导致电流拥挤，芯片的电光转化效率衰减严重。经过优化设计后的微结构阵列器件，具有较高的电注入效率，因此芯片的出光效率较高且随输入电流的增加而衰减的趋势较慢，因此更适合大电流下工作。

Light-output Enhancement of GaN-based Light-emitting Diodes with Surface Textured ITO

The sophisticated techniques of photolithography and wet-etching are used to fabricate GaN-based LED chips with surface-textured ITO layer to enhance the light output efficiency. It is shown that the light-output power can be efficiently improved by this surface-textured method. After the triangle-lattice of close-packed micro-holes are fabricated, the light-output power of LED chips under the injection current of 20 mA exhibits 11.4% enhancement comparing to the conventional LED chips. However, the forward voltage correspondingly increases 0.178 V. With our proposed micro-structures, the light-output power can also be enhanced by 8.2%, while the forward voltage increases only 0.044 V. It is also shown that the close-packed micro-hole pattern benefits high light-output under small injection current. However, this pattern would induce current-crowding if the injection current become high, and thus the light-output efficiency would decrease significantly. On the other hand, our optimized micro-structure is help for high electric-injection efficiency. This induces a high light-output efficiency, and the efficiency droop can be suppressed. The proposed micro-structure is preferred for high power LED chips under large current injection.