GeSe monolayer semiconductor with tunable direct band gap and small carrier effective mass

Two dimensional materials, befitting nanoscale electronics, can benefit strain-tunable applications due to their ultrathin and flexible nature. Based on the first-principles calculations within the generalized gradient approximation, GeSe monolayer with a distorted NaCl-type structure is predicted. The GeSe monolayer is found to be a direct semiconductor with a band gap of (1.16 ± 0.13) eV against the bulk counterpart. The electronic responses of the GeSe monolayer to strain are found to be sensitive and anisotropic, and the transitions between direct and indirect band gap are repeatedly met in the course of energy engineering by uniaxial and biaxial strains. The direct band gap of the GeSe monolayer is tunable by small strain within a large energy range (0.95–1.48 eV). The carrier effective masses in the GeSe monolayer are also tunable by strain in a low mass range (0.03–0.61 m0). These intriguing properties make GeSe monolayer a promising two-dimensional material for nanomechanics, thermoelectrics, and optoelectronics.