Effect of the native oxide on the Surface Passivation of Si by Al2O3

Abstract

The effect of the native silicon oxide layer on the passivation properties of Al2O3 on p-type Si surfaces has been investigated. This was done by comparing effective carrier lifetime, surface saturation current density, fixed charge, and density of interface states of samples, where the native oxide was not removed prior to Al2O3 passivation, with samples subjected to a 3 min HF-dip. The sample with the native oxide exhibits excellent surface passivation post-annealing, with a surface saturation current density of 13 fA/cm2 and significantly longer effective lifetime compared to the sample, where the native oxide was removed. Capacitance–voltage measurements of a sample with the native oxide revealed a remarkably low density of interface states (1010 eV−1 cm−2), almost three times lower than a sample where the native oxide was removed prior to Al2O3 deposition. The results indicate that a thin layer of native oxide improves the Al2O3 surface passivation of silicon.