Distribution of Excess Charge Carriers in Bilateral Macroporous Silicon with Different Thicknesses of Porous Layers

The paper presents a system of equations describing the distribution of excess charge carriers in bilateral macroporous silicon with different thicknesses of porous layers. The system contains equations, which are the general solution to the diffusion equation written for a monocrystalline substrate and each porous layer. Also, it contains equations describing the boundary conditions on two surfaces of a bilateral macroporous silicon sample and on the boundaries of a monocrystalline substrate with macroporous layers. It was taken into account that light propagates through the pores and illuminates the monocrystalline substrate through the bottom of the pores. We calculated the distribution of excess charge carriers in bilateral macroporous silicon with different thicknesses of porous layers, provided that excess charge carriers are generated by light with wavelengths of 0.95 and 1.05 m. At these wavelengths, the generation of excess charge carriers was uniform and non-uniform over the sample, respectively. The calculations were carried out for the cases when one layer of macropores had a thickness of 100 m, while the other varied from zero to 400 m. It is shown that one or two maxima are observed in the distribution of excess charge carriers in bilateral macroporous silicon with different thicknesses of porous layers. The maximum can be located near surfaces that are illuminated by light or in the middle of a monocrystalline substrate. The maxima decrease due to the diffusion of charge carriers to the recombination surfaces. The distribution of excess charge carriers in bilateral macroporous silicon with different thicknesses of porous layers is affected by the recombination of excess charge carriers on the pore surface of each macroporous layer and the diffusion of excess charge carriers from the substrate to the recombination surfaces in porous layers.