在4H-SiC基底上设计并制备了Al2O3/SiO2紫外双层减反射膜, 通过扫描电镜(SEM)和实测反射率谱来验证理论设计的正确性。利用编程计算得到Al2O3和SiO2的最优物理膜厚分别为42.0 nm和96.1 nm以及参考波长λ=280 nm处最小反射率为0.09％。由误差分析可知, 实际镀膜时保持双层膜厚度之和与理论值一致有利于降低膜系反射率。实验中应当准确控制SiO2折射率并使Al2O3折射率接近1.715。用电子束蒸发法在4H-SiC基底上淀积Al2O3/SiO2双层膜, 厚度分别为42 nm和96 nm。SEM截面图表明淀积的薄膜和基底间具有较强的附着力。实测反射率极小值为0.33％, 对应λ=276 nm, 与理论结果吻合较好。与传统SiO2单层膜相比, Al2O3/SiO2双层膜具有反射率小, 波长选择性好等优点, 从而论证了其在4H-SiC基紫外光电器件减反射膜上具有较好的应用前景。

Al2O3/SiO2 double-layer UV antireflection coatings were designed and fabricated on 4H-SiC substrate, and the validity of theoretical design was further verified by scanning electron microscope (SEM) and reflection spectrum. The optimal physical thickness of Al2O3 and SiO2 is 42.0 nm and 96.1 nm respectively by programming calculation. And then the minimum reflectance of 0.09% is obtained at reference wavelength λ=280 nm. According to error analysis, keeping the sum of double-layer thickness consistent with theoretical value is helpful to reduce the reflectance. In addition, the refractive index of SiO2 should more accurate and the refractive index of Al2O3 should be controlled close to 1.715 in the experiment. Al2O3/SiO2 double-layer coatings were deposited on 4H-SiC substrate by electron beam evaporation and the physical thickness is 42 nm and 96 nm respectively. SEM images show that the deposited layers and the substrate perform good adhesion to each other. The practical minimum reflectance is 0.33% at λ=276 nm which is close to theoretical value. Compared with conventional SiO2 single layer, Al2O3/SiO2 double-layer coatings show low reflectance and better wavelength selectivity. These results make the possibility for 4H-SiC based UV optoelectronic devices with Al2O3/SiO2 films as antireflection coatings.