Effect of annealing temperature on properties of SiO₂/Si₃N₄ optical films prepared by PECVD method

Abstract

Based on the basic principle and algorithm of multi-layer optical thin films, SiO2/Si3N4 double-layer antireflection films for three-junction reverse GaAs solar cells were prepared on GaAs substrate by plasma enhanced chemical vapor deposition (PECVD). The relationships between post-annealing and the morphology, structure and optical properties of the multilayer films were characterized by atomic force microscope (AFM), Fourier transform infrared spectrometer (FT-IR), elliptical polarizer, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometer. The results indicate that the films are crystalline state both before and after annealing. With the increase of annealing temperature, the roughness and average reflectance gradually decrease. SiO2/Si3N4 films annealed at 700 ℃ have the best performance with the lowest average reflectance of 12.65% and roughness of 1.64 nm. The spectral curve of the films move towards to short-wave direction about 30 nm, showing a typical "blue-shift" phenomenon, which indicates that the optical thickness of the films demonstrates a declining trend with the rising of annealing temperature.

Keywords

• antireflection film
• gaas-based solar cell
• plasma enhanced chemical vapor deposition
• annealing