Monolayer MoS2/GaAs heterostructure self-driven photodetector with extremely high detectivity

Two dimensional material/semiconductor heterostructures offer alternative platforms for optoelectronic devices other than conventional Schottky and p–n junction devices. Herein, we use MoS 2 /GaAs heterojunction as a self-driven photodetector with wide response band width from ultraviolet to visible light, which exhibits high sensitivity to the incident light of 635   nm with responsivity as 321   mA/W and detectivity as 3.5×10 13   Jones (Jones=cm   Hz 1/2   W −1 ), respectively. Employing interface design by inserting h-BN and photo-induced doping by covering Si quantum dots on the device, the responsivity is increased to 419   mA/W for incident light of 635   nm. Distinctly, attributing to the low dark current of the MoS 2 /h-BN/GaAs sandwich structure based on the self-driven operation condition, the detectivity shows extremely high value of 1.9×10 14   Jones for incident light of 635   nm, which is higher than all the reported values of the MoS 2 based photodetectors. Further investigations reveal that the MoS 2 /GaAs based photodetectors have response speed with the typical rise/fall time as 17/31   μs. The photodetectors are stable while sealed with polymethyl methacrylate after storage in air for one month. These results imply that monolayer MoS 2 /GaAs heterojunction may have great potential for practical applications as high performance self-driven photodetectors.