INFLUENCE OF SURFACE COVERAGE ON THE EFFECTIVE OPTICAL-PROPERTIES OF POROUS SILICON MODELED AS A SI-WIRE ARRAY

The effective dielectric function, effective absorption coefficient an d effective refractive index for a model of porous silicon (PS) are ca lculated using the volume and surface averaging method. The model cons ists of periodic Si wires with different surface coverages. This appro ach allows to obtain analytical results within certain approximations. The method uses experimental parameters to characterize the bulk and the surface. We choose the bulk c-Si, and cover it with three differen t possible surface skins: siloxanes, a-Si:H and SiO2. The results are compared with PS experimental data and other theoretical approaches fo r silicon wires. We obtain good agreement for certain coatings. Our re sults emphasize the important role of surface coatings in the effectiv e response of porous silicon. (C) 1997 American Institute of Physics.