All-fiber-integrated photodetector with low dark current and fast response based on a Cu-MgF2-FA0.4MA0.6PbI3 metal-insulator-semiconductor structure

All-fiber-integrated photodetectors (AFPDs) have low coupling loss with current main-stream optical fiber system, and exhibits an ultra-high photoresponsivity at low optical radiation energy. Most AFPDs are meal-semiconductor-metal (MSM) structure, and the work function difference between metal and semiconductor is small, it will produce a larger dark current. The susceptibility to undesirable chemical reactions between the metal and semiconductor interfaces, which limits the performance of devices. In the pa-per, an AFPD based on Cu-MgF2-FA0.4MA0.6PbI3 metal-insulator-semiconductor (MIS) structure were proposed. The MgF2 insulating layer inserted between the Cu electrode and the perovskite not only improves the undesirable reaction between Cu and perov-skite, but also raises the potential barrier at the metal-semiconductor contact interface, thus, the dark current is effectively reduced. The MIS structure also has a strong built-in electric field that reduces the transit time of the photogenerated carriers, which enhances the response speed of the device. The experimental results show that the device dark current can reach a minimum of 8.79×10-10 A at -1 V bias voltage, which is approximate-ly 106 orders of magnitude lower than that of previously reported devices. The photo-to-dark current ratio is 84. The response time of the device on the rising and falling edges is 8.8 ms and 2.5 ms, respectively. The response of the device can reach 0.69 A/W. The proposed device has the advantages of high stability, low dark current, short response time and all-fiber integration. It provides a reliable solution for the development of high-performance AFPDs.