Calculated Forbidden Bandgap of Si₃MnS Phase in Supercell (1Х1Х3) and Experimentally Determined Forbidden Bandgap of Si<MnS>

The paper presents the results of a quantum chemical calculation of a hypothetical Si3MnS structure representing a “hybrid” of the cubic lattice of silicon Si and sphalerite ZnS. The Si lattice with a diamond structure, scaled up to a supercell (1X1X3), has been chosen for further study and calculation. Several assumptions have been made regarding the most likely substitutional sites for S and Mn impurity atoms in the Si crystal lattice. The corresponding Si3MnS phase is expected to form in the first coordination shell. For quantum chemical calculations, the Quantum ESPRESSO suite for first-principles electronic-structure calculations and materials modeling has been adopted. The calculated forbidden bandgap of Si3MnS phase in a (1х1х3) supercell turns out to be 1.14 eV. Also, the current-voltage characteristics of Si<Mn,S> samples with p-n junction have been measured by applying the technique of temperature scanning at two comparatively low and nearly adjacent temperatures with the aim to determine the experimental forbidden bandgap energy value. The original n-type single-crystal silicon (phosphor-doped, specific resistance 100 Ω·cm) and p-type single-crystal silicon (boron-doped, specific resistance 1 Ω·cm) were used as initial materials for the experiments. An attempt has been made to perform a comparative analysis of forbidden bandgap values determined both during quantum-chemical calculations of the density of electronic states of the Si3MnS phase and during experimental measurements. Thorough quantum chemical calculations of IV/III-V and IV/II-VI-type “hybrid” structures in the cubic lattice of silicon and experimental measurements could incidentally shed light onto the possibility of engineering high-performance structures for future solar cells based on single crystal silicon.

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