Abstract
Macroporous silicon has found applications in sensors, receivers, integrated microchips and solar cells. In this work, we first showed analytically the photoconductivity relaxation time of in macroporous silicon is determined from a system of two transcendental equations. The analytical description of the photoconductivity relaxation model contains the diffusion equation solution both in single crystal substrate and in an effective medium of macroporous layer, as well as boundary conditions recorded for the surfaces of the layer of macroporous silicon and single crystal substrate. We showed that the photoconductivity relaxation time in macroporous silicon rapidly decreases with increasing macropore depth from 0 to 25 μm and reduced thicknesses of the single crystal substrate from 250 to 0 μm. The photoconductivity recombination time in the sample of macroporous silicon is limited by the diffusion of charge carriers from the substrate to the recombination surfaces in the macroporous layer. The system of transcendental equations that we have found will find application in calculating the relaxation time of photoconductivity in macroporous silicon devices such as sensors, receivers, and solar cells.
Highlights
Macroporous silicon is used in microelectronics, optics and optoelectronics due to its simplicity of manufacture, structural and physical properties, and the possibility of integration into microcircuits
Photoconductivity relaxation time in macroporous silicon decreases rapidly if the depth of the macropores increases from 0 to 25 μm. This rapid decrease in relaxation time is due to the fact that the area of recombination surfaces in the macroporous silicon layer increases with increasing the depth of the macropores
The first equation describes the diffusion of excess charge carriers and their recombination in a layer of macroporous silicon and recombination at the interface of the layer of macroporous silicon and the single crystal substrate
Summary
Macroporous silicon is used in microelectronics, optics and optoelectronics due to its simplicity of manufacture, structural and physical properties, and the possibility of integration into microcircuits. A layer of macroporous silicon improves the absorption of light; it has found application in solar cells [1, 2]. Theoretical model calculates the efficiency of a textured silicon solar cell depending on its thickness [4]. She considers two mechanisms that determine the optimal thickness of a solar cell. The surface of macroporous silicon is oxidized to reduce recombination on the surface and increase the lifetime of excess charge carriers [8]. The effective lifetime of minority charge carriers in macroporous silicon with a macroporous layer on each side is determined from a system of two transcendental equations. Numerical modeling showed that Lambertian light trapping is the predominant absorption mechanism in the band gap region [20]
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