Surface Passivation of Crystalline Silicon by Combination of Amorphous Silicon Deposition with High-Pressure H2O Vapor Heat Treatment

概要

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A high minority carrier effective lifetime \tau_{\text{eff}} of crystalline silicon was achieved by hydrogenated amorphous silicon (a-Si:H) films formed by a combination of plasma-enhanced chemical vapor deposition at 150 °C with high-pressure H2O vapor heat treatment. \tau_{\text{eff}} was 1.6\times 10^{-4}, 3.0\times 10^{-4}, and 1.15\times 10^{-3} s for n-type silicon substrates coated with 3-, 10-, and 50-nm-thick a-Si:H films treated with 1.0\times 10^{6} Pa H2O vapor heat treatment between 180 and 300 °C for 1 h. Light-induced passivation enhancement was demonstrated when 620-nm light was illuminated at the 50-nm-thick a-Si:H surface. \tau_{\text{eff}} increased from 8.5\times 10^{-4} to 1.15\times 10^{-3} s probably caused by field effect passivation induced by hole trapping at the SiOx formed by H2O vapor heat treatment for 1 h. On the other hand, \tau_{\text{eff}} was further increased to 1.2\times 10^{-3} s by 1.0\times 10^{6} Pa H2O vapor heat treatment at 300 °C for 3 h for the sample formed with the 50-nm-thick a-Si:H film. However, no increase in \tau_{\text{eff}} was observed by light illumination at the a-Si:H surface, probably because the SiOx clusters became stable and had no hole trapping property.
2012-03-25