Electron Transfer Mechanism and Nonlinear Optical Properties of Ga2O3/MoS2 Nanoheterostructures: Implications for Optoelectronic Devices

Manipulating and optimizing the pathway of the interfacial and band engineering for MoS2 with excellent nonlinear absorption and dynamics are very important for two-dimensional semiconductor optoelectronic device technology in the future. However, the application of MoS2 in many optical devices has been seriously limited by the electron transfer and carrier regulation. Herein, designing Ca2O3 combined with MoS2 was used to solve the problems of the narrow absorption band range and low efficient photoelectric transfer of the MoS2 material. Ga2O3/MoS2 (GMS) nanoheterostructures with a type I energy band arrangement were prepared by a two-step hydrothermal/magnetron sputtering method. The dependence of experimental parameters on the structural characteristics of samples is discussed. The analysis of Raman and X-ray photoelectron spectroscopy (XPS) indicated the electron transfer between MoS2 and Ga2O3. The results of X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) characterization further indicate that the VB edge and CB edge of MoS2 are located within the band gap of Ga2O3, forming an I-type GMS nanoheterostructure. Photoluminescence and ultraviolet absorption results show that the transfer of electrons from Ga2O3 to MoS2 enhances the electron–hole recombination of MoS2. The Z-scan results show that the nonlinear absorption of GMS nanoheterostructures changes from saturable absorption to reverse saturable absorption. The nonlinear absorption properties of GMS nanoheterostructures could be attributed to the competition between the ground- and excited-state absorption. Transient absorption measurements confirmed that the ultrafast, fast, and slow carrier processes of GMS nanoheterostructures were attributed to the redistribution of electrons in the excited state and the bottom of the conduction band, the relaxation of electrons from the excited state to the defect state, and the three processes of interband relaxation, respectively. The research has some repercussions for MoS2 and Ga2O3 nanoheterostructures with rich band gap and interfacial charge transfer engineering and obtaining highly efficient charge transfer photoelectric functional materials, which are promising materials for improving nonlinear optic properties in photonic devices and optoelectronic applications.