Fast, Self-Driven, Air-Stable, and Broadband Photodetector Based on Vertically Aligned PtSe₂/GaAs Heterojunction

Group-10 layered transitional metal dichalcogenides including PtS ₂, PtSe ₂, and PtTe ₂ are excellent potential candidates for optoelectronic devices due to their unique properties such as high carrier mobility, tunable bandgap, stability, and flexibility. Large-area platinum diselenide (PtSe ₂) with semiconducting characteristics is far scarcely investigated. Here, the development of a high-performance photodetector based on vertically aligned PtSe ₂-GaAs heterojunction which exhibits a broadband sensitivity from deep ultraviolet to near-infrared light, with peak sensitivity from 650 to 810 nm, is reported. The I _light/I _dark ratio and responsivity of photodetector are 3 × 10 ⁴ and 262 mA W ⁻¹ measured at 808 nm under zero bias voltage. The response speed of τ _r/τ _f is 5.5/6.5 µs, which represents the best result achieved for Group-10 TMDs based optoelectronic device thus far. According to first-principle density functional theory, the broad photoresponse ranging from visible to near-infrared region is associated with the semiconducting characteristics of PtSe ₂ which has interstitial Se atoms within the PtSe ₂ layers. It is also revealed that the PtSe ₂/GaAs photodetector does not exhibit performance degradation after six weeks in air. The generality of the above good results suggests that the vertically aligned PtSe ₂ is an ideal material for high-performance optoelectronic systems in the future.