I. Mihalcescu et al., SURFACE PASSIVATION - A CRITICAL PARAMETER FOR THE VISIBLE LUMINESCENCE OF ELECTROOXIDIZED POROUS SILICON, Journal of luminescence, 57(1-6), 1993, pp. 111-115
It is shown that the passivation of the internal surface of pores dete
rmines not only the intensity but also the spectral dependence of the
luminescence. Anodic oxidation is used as a method of passivation and
thinning of the porous structure, it enables us to follow the evolutio
n of the photoluminescence, decay times and electroluminescence. Since
the room temperature luminescence is dominated by the non-radiative r
ecombination on the surface, we introduce a model with two types of cr
ystallites depending on their surface passivation. For the perfectly p
assivated crystallites, we describe the non-radiative recombination me
chanism as carriers escaping by tunnelling through the surrounding pot
ential barriers of the crystallite. This model is able to explain at t
he same time the PL and EL evolution during anodic oxidation as well a
s the form of the decay times and their wavelength dependence.