Strain enhancement for a MoS 2 -on-GaN photodetector with an Al 2 O 3 stress liner grown by atomic layer deposition

Strain regulation as an effective way to enhance the photoelectric properties of two-dimensional (2D) transition metal dichalcogenides has been widely employed to improve the performance of photovoltaic devices. In this work, tensile strain was introduced in multilayer MoS 2 grown on GaN by depositing 3 nm of Al 2 O 3 on the surface. The temperature-dependent Raman spectrum shows that the thermal stability of MoS 2 is improved by Al 2 O 3 . Theoretical simulations confirmed the existence of tensile strain on MoS 2 covered with Al 2 O 3 , and the bandgap and electron effective mass of six layers of MoS 2 decreased due to tensile strain, which resulted in an increase of electron mobility. Due to the tensile strain effect, the photodetector with the Al 2 O 3 stress liner achieved better performance under the illumination of 365 nm wavelength, including a higher responsivity of 24.6 A/W, photoconductive gain of 520, and external quantum efficiency of 8381%, which are more than twice the corresponding values of photodetectors without Al 2 O 3 . Our work provides an effective technical way for improving the performance of 2D material photodetectors.