Bandgap-Engineered pSi/n-CdₓS₁₋ₓ Heterojunctions: Effect of Composition on Optoelectronic Behavior

This study provides a comprehensive analysis of the electrophysical properties of the pSi/n-CdₓS₁₋ₓ heterojunction, where the cadmium composition x varies continuously from 0 to 1. The investigation integrates theoretical modeling, numerical simulations, and experimental validation employing typical doping concentrations of p = 2 × 10¹⁷ cm⁻³ for p-type porous silicon and n = 1 × 10¹⁸ cm⁻³ for n-type CdₓS₁₋ₓ. Particular attention is devoted to the temperature-dependent evolution of key material parameters, including the bandgap energy Eg(T), intrinsic carrier concentration nᵢ(T), and the Debye temperature Θ(x). As the cadmium fraction increases, the bandgap narrowing in CdₓS₁₋ₓ becomes evident, while porous silicon maintains a relatively wide and thermally stable Eg(T), resulting in a substantial band offset (ΔEg) that enhances charge carrier separation across the interface. Furthermore, the reduction of Θ(x) with increasing cadmium concentration modulates phonon scattering and recombination dynamics, thereby influencing charge transport characteristics. The analysis of current transport mechanisms indicates that the junction behavior is predominantly controlled by temperature- and composition-dependent band alignment and carrier recombination processes. The obtained results validate the proposed physical model and demonstrate the promising potential of pSi/n-CdₓS₁₋ₓ heterostructures for high-temperature and acoustically tunable optoelectronic devices.

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