Negative charge and charging dynamics in Al2O3 films on Si characterized by second-harmonic generation

Thin films of Al2O3 synthesized by atomic layer deposition provide an excellent level of interface passivation of crystalline silicon (c-Si) after a postdeposition anneal. The Al2O3 passivation mechanism has been elucidated by contactless characterization of c-Si/Al2O3 interfaces by optical second-harmonic generation (SHG). SHG has revealed a negative fixed charge density in as-deposited Al2O3 on the order of 10(11) cm(-2) that increased to 10(12)-10(13) cm(-2) upon anneal, causing effective field-effect passivation. In addition, multiple photon induced charge trapping dynamics suggest a reduction in recombination channels after anneal and indicate a c-Si/Al2O3 conduction band offset of 2.02 +/- 0.04 eV. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2985906]