Polarization-enhanced ultrafast carrier transfer dynamics in Ga2O3/WS2 heterojunctions

Abstract

Polarization engineering offers a promising strategy to enhance photogenerated carrier separation in van der Waals heterojunctions. Herein, the mechanisms governing polarization-enhanced carrier separation in Ga2O3/WS2 are investigated using nonadiabatic molecular dynamics. The results indicate that nearly 46% of the electrons transfer from WS2 to Ga2O3 within 321 fs in Ga2O3↓/WS2, whereas approximately 15% of the holes transfer in the opposite direction within 50 fs. The asymmetric carrier dynamics suggest transient redistribution of photoexcited carriers between the two layers. These transfer dynamics are associated with several phonon features in the Fourier transform spectra. In comparison, photoexcited charge transfer in Ga2O3↑/WS2 occurs on a timescale of 82 fs, owing to the type-III band alignment with a narrow gap of 0.12 eV. These findings indicate that the introduction of intrinsic polarization modulates the electronic properties and enhances photoexcited carrier separation of Ga2O3/WS2.