Surface passivation performances of Al2O3layers deposited on p-type Czochralski Si wafers by atomic layer deposition(ALD) were investigated as a function of post-deposition annealing conditions.The maximal minority carrier lifetime of4.7 ms was obtained for AI2O3passivated p-type Si.Surface passivation mechanisms of Al2O3layers were investigated in terms of interfacial state density(Dit) and negative fixed charge densities(Qfix) through capacitance—voltage(C— V) characterization.High density of Qfixand low density of Ditwere needed for high passivation performances,while high density of Ditand low density of Qfixdegraded the passivation performances.A low Ditwas a prerequisite to benefit from the strong field effect passivation induced by high density of negative fixed charges in the Al2O3layer.