光子晶体提高GaN基LED发光效率实验与工艺研究

Improvement of Luminous Efficiency of GaN-based LEDs Using Photonic Crystal

采用聚焦离子束制备了500nm和1.5μm周期两种结构,使GaN基LED光效显著提高。比较长、短周期光子晶体提高光效的程度、制备工艺、设备及其相应的成本,宜采用长周期光子晶体结构来提高蓝光GaN基LED的发光效率。采用聚焦离子束和激光干涉两种方法,在GaN基LED导电层(ITO)上制备了长周期光子晶体,利用光纤光谱仪、显微镜和功率计对光提取效率进行了实验测试,结果表明长周期光子晶体LED比无光子晶体LED的光提取效率提高了90%以上。还采用激光干涉直写方法,以扫描的方式在较大面积上制备了光子晶体LED,确认了该方法及工艺批量化、低成本制备光子晶体的可行性。聚焦离子束方法虽然能够产生较精确的光子晶体图形,但由于耗时长、效率低、成本高等问题,仅适于在实验研究中选择和优化光子晶体的结构和参数。

Two kinds of periodical structures with period of 500 nm or 1.5 μm were fabricated by using focused ion beam（FIB）.Comparing the enhancing lighting effects,processes,equipments and costs of the two kinds of photonic crystal,it is found that the photonic crystal structure with longer period（1.5 μm） is suitable for improving the luminous effect of blue GaN-based LEDs.In this work,applying FIB and laser interference method,LEDs with long period photonic crystal structure were prepared on the electric conductive coating（ITO） on the substrate of GaN.Then measured by fiber spectrometer,microscope and power meter,it is shown that,compared with normal LED without photonic crystal,the light extracting efficiency improves by more than 90%.Using the method of direct writing with laser-interfering-patten,photonic structure was made on larger area with the scanning laser spot,confirming the feasibility of the process in large scale and at low cost.The FIB method is suitable for choosing and optimizing the structure and parameters of the photonic crystal in experiments,due to its low efficiency,time consuming and high cost.