Band gap transition characteristics for emission on (GeSn)n/Si superlattice

Abstract

Explorations in Group IV materials reveal the optic-electronic tunability enhanced in the GeSn/Si superlattices through synergistic controlling strain and quantum confinement effects, where the combination system of Ge nanolayer to produce pumping states and GeSn superlattices for generating emission states is built, positioning them as promising candidates for monolithically integrated silicon photonics. However, the fundamental mechanisms governing bandgap modulation and emission enhancement in these systems remain insufficient, primarily due to experimental challenges in achieving atomic-level periodicity control under metastable growth conditions. The Density Functional Theory (DFT) is used to perform first-principles calculations, in which the electronic structure of (GeSn)_n/Si superlattice with less than 8 % Sn atom doping is systematically investigated, and the Ge/Si nanolayer without Sn atom doping for comparative analysis is calculated. The calculation results show that the direct band gap of (GeSn)_n/Si superlattice (period n: 1 to 5) varies from 0.426 eV to 0.033 eV, and the direct band gap of Ge/Si nanolayer varies from 0.657 eV to 0.263 eV in the diameter variation range of 1.67 nm to 6.10 nm, which are originated from the quantum confinement effect and the tensile strain effect. Therefore, the computational insights establish a predictive framework for optimizing relevant experiments, which is conducive to realizing silicon-based light sources.