On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

Al2O3 is a versatile high-kappa dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high- efficiency solar cells. We demonstrate both experimentally and by simulations that the surface passivation can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density Q(f) of up to 10(13) cm(-2) present in the Al2O3 film at the interface with the underlying Si substrate. The negative polarity of Qf in Al2O3 is especially beneficial for the passivation of p-type c-Si as the bulk minority carriers are shielded from the c-Si surface. As the level of field-effect passivation is shown to scale with Q(f)(2), the high Q(f) in Al2O3 tolerates a higher interface defect density on c-Si compared to alternative surface passivation schemes. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3021091]