Preparation of a Novel Al2O3/SiO2/Nano-SiO2 ARC on GaAs Wafer with Broadband Spectrum

Abstract

In the paper, a novel Al2O3/SiO2/Nano-SiO2 triple-layer antireflection coating (ARC) on GaAs wafer with lower reflectance range on broadband spectrum was developed by sol-gel method. The experiments showed that: (1) to obtain stable and transparent liquid Al2O3 sol, the three crucial factors the concentration of aluminum isopropoxide, hydrolysis temperature and reflux time should be controlled well, which could be 0.68~1.04mol/L, 90~95℃, and longer than 10h respectively. (2) The Al2O3 film and SiO2 film would be thicker with the acceleration of withdrawal speed, be thinner with the rising of annealing temperature; and the refractive index would be lower with the rising of annealing temperature also. (3) The Al2O3 film would put forward Boehmite (γ-AlOOH) structure after 200℃ annealing; while when the annealing temperature was higher than 200℃, the film showed γ- Al2O3 phase, with refractive index 1.71, and film thickness could be adjustable from 74.1 nm to 161 nm.(4) The amorphous SiO2 thin-film could be adjustable also, which refractive index ranged from 1.21 to1.45, thickness varied from 132.8nm to 219nm.