Study of WO 3 -decorated porous silicon and Al 2 O 3 -ALD encapsulation

In this work, we report on the encapsulation of WO 3 -decorated porous silicon aluminum oxide (Al 2 O 3 ). Porous layers, elaborated for different current densities, are decorated by quasi-spherical WO 3 nanoparticles with different densities and sizes. AFM analysis shows that the WO 3 deposition is controlled by the prepared porous silicon morphology. WO 3 -treated porous silicon samples were faithfully coated by ALD-Al 2 O 3 . A significant enhancement of porous silicon reflectance after AL 2 O 3 /WO 3 deposition was obtained. In order to quantify the passivation effect of the dual treatment, the effective diffusion length (L eff ) of the minority carriers is determined by Light Beam Induced Current (LBIC) measurements. An increase of L eff from 74 µm in porous silicon to 532 µm in AL 2 O 3 /WO 3 /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.