Investigation on temperature-dependent optoelectronic properties of MoSe₂ nanosheet/Si heterojunction photodetectors

MoSe₂ nanosheet/Si heterojunction photodetectors were fabricated by a mechanical exfoliation method, and their electrical and optical properties at different temperatures were investigated. It was found that the MoSe₂ nanosheet/Si heterojunction device exhibited excellent rectification characteristics at room temperature, and the rectification ratio gradually decreased with the decrease of temperature. The temperature-dependent electrical properties of the MoSe₂/Si heterojunction device were actually caused by the inhomogeneity of the potential barrier. Under illumination with blue light (405 nm, 0.301 W cm^-2) and red light (650 nm, 0.122 W cm^-2), the heterojunction device showed obvious photocurrent responses. Under blue light illumination, the responsivity was 53.7 A W^-1, the detectivity was 8.32 × 10¹¹ Jones, the external quantum efficiency (EQE) was 1.64 × 10⁴%, and the maximum photocurrent on-off ratio was 1250. Under red light illumination, the responsivity was 65.9 A W^-1, the detectivity was 1.02 × 10¹² Jones, the EQE was 1.26 × 10⁴%, and the maximum photocurrent on-off ratio was 623. In addition, the temperature-dependent measurements revealed that the rise and fall times of the heterojunction device under different wavelengths of light illumination monotonically increased with the decrease of temperature.