Ultrasensitive Ferroelectric Semiconductor Phototransistors for Photon‐Level Detection.

Low‐light‐level photodetections are highly desired in the fields of astronomy and quantum information. However, the existing techniques suffer from high operation voltages and complexity of fabrication, which reduces its compatibility with complementary metal oxide semiconductors (CMOS) based read‐out circuit and prevent the use of imaging. Here, a low‐light‐level phototransistor that employs a photo‐induced ferroelectric reversal mechanism in a ferroelectric semiconductor channel: α‐In2Se3 is demonstrated. It shows a record‐low noise‐equivalent power of 7.9 × 10−22 W Hz−1/2, a record‐high specific detectivity of 6.34 × 1017 Jones, and sensitivity approaching 20 photons in a photon‐counting mode, and fast time response of 260 µs/50 ns in the rise/decay period. It also works as an optoelectronic memory with an on/off ratio of 2.9 × 105, retention of longer than 10 years, and endurance of more than 106 cycles. Due to its high performance, simple architecture, and small operation voltage, the phototransistor provides a feasible platform for new‐generation low‐light‐level image sensors. [ABSTRACT FROM AUTHOR]