On the Semiconductor Spectroscopy for Identification of Emergent Contaminants in Transparent Mediums

In this chapter, we present a theoretical study of photoelectronic processes in experimental silicon n⁺- p- n⁺ structures with applications in identifying emergent contaminants in aqueous medium. Contribution due to various mechanisms of photon absorption to the total photocurrent is calculated. Various mechanisms, such as the influence of tunneling on the spectral characteristic and selective spectral photosensitivity of samples under investigation were investigated. The nature of the relationship between energy parameters of the absorbed waves and the structural parameters is revealed. Expressions are obtained for photocurrent with and without external diffusion current due to potential silicide barriers arising from p-n junction or n⁺- p- n⁺ structures. We also calculate expressions for the absorption coefficient. In some samples, the injection of electrons through the direct-mesh n-p junction and the enhancement of the spectral photocurrent was observed. In samples without injection amplification of the photocurrent, an inversion of the sign of the spectral photocurrent took place. The inversion point is linear with the offset voltage, which can be used to find the unknown wavelength. Mutually compensating transitions in silicon structures provide shift of the maximum of the spectral photosensitivity from an intrinsic (~850 nm) to the short-wavelength region ~590 nm and 530 nm. The study suggests that, with the choice of structural parameters, it is possible to obtain different short-wavelength spectral maxima more accurately for a specific application such as for new and emergent contaminants in aqueous medium.