占空比可调的氮化镓纳米圆台阵列的制备及其光致发光效率的研究

Fabrication of Ga N Nano-Pillar Arrays with Tunable Duty Ratio and Study on Its Photoluminescence Efficiency

实验中在p-Ga N层制备单层密排的聚苯乙烯(PS)纳米球作为掩模,通过改变纳米球掩膜的直径,制作了周期性的占空比不同的Ga N纳米圆台阵列结构。实验结果表明,在归一化激发光功率后,p-Ga N层制备纳米圆台阵列的LED出光效率最高增加到参考样品的3.8倍。三维时域有限差分方法计算表明,周期性纳米结构破坏了p-Ga N表面的全反射,增大了LED结构的光输出临界角,从而提高LED的光致发光效率。此外,利用可变的纳米球掩模刻蚀技术,可以在同一个周期下优化纳米圆台的尺寸从而进一步提高LED的出光效率,这可以用等效折射率与薄膜透射率理论来解释,计算结果与实验结果比较一致。

A monolayer closely-packed polystyrene （PS） nanosphere is prepared as mask on p-GaN substrate in the experiment. The structures of GaN nano-pillar arrays with periodic different duty ratios are prepared by changing the diameter of nanosphere mask. The experiment results show that the photoluminescence efficiency of LED of nano-pillar arrays prepared on p-GaN substrate can be raised to 3.8 times of the reference sample after normalizing power of the laser. The three-dimensional finite difference time domain simulation shows that photoluminescence efficiency is enhanced because the periodic nano structure breaks total reflection of GaN surface, and critical angle of light output of LED structure is enlarged. In addition, we can optimize the size of nano-pillar in the same period to improve photoluminescence efficiency of LED further by changeable nanosphere mask lithography. It can be explained by effective refractive index theory and film transmittance. The theoretical and calculated results are in agreement with the experimental results.