Theoretical and experimental investigation of nano-materials based on Ge–Mn for third-generation solar cells

This paper presents a theoretical and experimental investigation into the electronic and optoelectronic properties of ultra-pure crystalline GeMn quantum dots (QDs) embedded in a silicon dioxide matrix. GeMn QDs were grown by high-precision solid-source molecular beam epitaxy (SSMBE) on tunnel thermal silicon oxide using a solid-state dewetting process and were capped with a PECVD thin oxide layer. GeMn quantum dots of three distinct sizes and Mn concentrations have been grown. Atomic force microscopy (AFM), Raman, high-resolution transmission electronic microscopy (HRTEM), and photocurrent spectroscopies are utilized to characterize the refined samples. To calculate the electronic structures of GeMn nanostructures, a theoretical model that incorporates strain-dependent effects has also been developed. Expanding the shell wave function with Bessel functions, we calculate the energies of the exciton states in GeMn/SiO2 QDs. The experimental findings indicate that the QDs produced by this new method are homogeneous, extremely dense, and crystalline, with the Mn perfectly incorporated into the Ge matrix. Moreover, photocurrent measurements performed on these QDs have demonstrated, as predicted by theoretical calculations performed on these QDs, that these magnetic QDs are extremely sensitive to visible light. When these QDs are illuminated with visible light, the photocurrent increases by more than tenfold. These significant theoretical and experimental results demonstrate that GeMn quantum dots produced by solid-state dewetting can be combined with photonic and optoelectronic technologies to produce third-generation solar cells and spin-optoelectronic devices with enhanced efficiency.