High photosensitivity and broad spectral response of multi-layered germanium sulfide transistors

In this paper, we report the optoelectronic properties of multi-layered GeS nanosheet (∼28 nm thick)-based field-effect transistors (called GeS-FETs). The multi-layered GeS-FETs exhibit remarkably high photoresponsivity of R λ ∼ 206 A W −1 under 1.5 μW cm −2 illumination at λ = 633 nm, V g = 0 V, and V ds = 10 V. The obtained R λ ∼ 206 A W −1 is excellent as compared with a GeS nanoribbon-based and the other family members of group IV-VI-based photodetectors in the layered-materials realm, such as GeSe and SnS 2 . The gate-dependent photoresponsivity of GeS-FETs was further measured to be able to reach R λ ∼ 655 A W −1 operated at V g = −80 V. Moreover, the multi-layered GeS photodetector holds high external quantum efficiency (EQE ∼ 4.0 × 10 4 %) and specific detectivity ( D * ∼ 2.35 × 10 13 Jones). The measured D * is comparable to those of the advanced commercial Si- and InGaAs-based photodiodes. The GeS photodetector also shows an excellent long-term photoswitching stability over a long period of operation (>1 h). These extraordinary properties of high photocurrent generation, broad spectral range, and long-term stability make the GeS-FET photodetector a highly qualified candidate for future optoelectronic applications. We report a multi-layered GeS nanosheet-based field-effect transistor of very high photoresponsivity, external quantum efficiency, and specific detectivity.