Analysis of the Surface Passivation Mechanisms of p-Doped Crystalline Silicon by Two Different Al₂O₃ Coatings via Transient Photo-Conductance Measurements

Abstract

In this paper, contactless transient photo-conductance measurements are applied to p-doped mono-crystalline Silicon (p-Si) coated by two different kinds of aluminum oxide (Al 2 O 3 ) layers in order to study alternative routes to the standard atomic layer deposition (ALD). The aluminum oxides layers were deposited by either spin coating or ion layer gas reaction (ILGAR ? ). For both coatings an increase of the charge carrier life time is observed indicating a passivation of the p-Si surface. This study shows alternative deposition methods and the potential of transient photocon- ductance measurements for the elucidation of the origin of the passivation. We show that the passivation induced by coating deposited via ILGAR is at least partially due to charge carrier trapping and storage at the interface. It was also surprisingly found that for those coatings, annealing at 425 ℃ leads to a decrease of the life time. This points to temperature instability for both coatings.