Surface Passivation Performance of Atomic-Layer-Deposited Al2O3 on p-type Silicon Substrates

Surface passivation performances of Al2O3 layers 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 of ∼4.7 ms was obtained for Al2O3 passivated p-type Si. Surface passivation mechanisms of Al2O3 layers were investigated in terms of interfacial state density (Dit) and negative fixed charge densities (Qfix) through capacitance–voltage (C–V) characterization. High density of Qfix and low density of Dit were needed for high passivation performances, while high density of Dit and low density of Qfix degraded the passivation performances. A low Dit was a prerequisite to benefit from the strong field effect passivation induced by high density of negative fixed charges in the Al2O3 layer.