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Surface passivation and antireflectance performances for atomic-layer-deposited Al2O3 films

Al2O3 films were deposited on single crystalline silicon wafers by atomic layer deposition. Both passivation and antireflectance performances are studied in detail. 30 nm Al2O3 passivated n-type and p-type Si shows a maximum effective minority carrier lifetime (τeff) of ∼5.2 ms and ∼4.7 ms, corresponding to a low surface recombination velocity of ∼3.8 cm s−1 and ∼4.2 cm s−1, respectively. By drawing a contour map of post-deposition annealing (PDA) temperature, PDA time and τeff, a wide PDA window is obtained for obtaining good passivation performances. The excellent passivation performances are related to the large, negative fixed charge density within Al2O3 films and the formation of interfacial SiO2 layer at the Al2O3/Si interface. Antireflectance performances are also studied in detail for Al2O3 and Al2O3/SiNx double-layer on textured Si. For obtaining a low average reflectance between 2.6% and 3%, a wide film-thickness window of ∼30 nm for Al2O3 and SiNx layer is observed for Al2O3/SiNx double-layer on textured Si. Our results indicate that Al2O3 films have excellent surface passivation and antireflectance performances with a wide processing window, which is favorable for c-Si solar cell applications.