Study of WO3-decorated porous silicon and Al2O3-ALD encapsulation

Abstract

In this work, we report on the encapsulation of WO3-decorated porous silicon aluminum oxide (Al2O3). Porous layers, elaborated for different current densities, are decorated by quasi-spherical WO3 nanoparticles with different densities and sizes. AFM analysis shows that the WO3 deposition is controlled by the prepared porous silicon morphology. WO3-treated porous silicon samples were faithfully coated by ALD-Al2O3. A significant enhancement of porous silicon reflectance after AL2O3/WO3 deposition was obtained. In order to quantify the passivation effect of the dual treatment, the effective diffusion length (Leff) of the minority carriers is determined by Light Beam Induced Current (LBIC) measurements. An increase of Leff from 74 µm in porous silicon to 532 µm in AL2O3/WO3/PS sample is reached. This enhancement is attributed to the dangling bonds saturation by alumina and tungsten oxide which leads to the diminution of the surface recombination velocities.