Self-Biased Phototransistor with Both Ultralow Dark Current and Fast Response

Infrared phototransistors have emerged as critical components in next-generation optoelectronic integrated circuits owing to their ultra-high responsivity. However, the high carrier concentration inherent in narrow-bandgap infrared materials poses significant challenges in suppressing dark current in room-temperature infrared phototransistors. Conventional strategies for reducing dark current, such as constructing heterojunctions, often compromise response speed. Here, a self-biased phototransistor (SBPT) architecture is reported capable of simultaneously achieving ultrahigh responsivity, ultrafast response speed, and ultralow dark current in infrared photodetection. This architecture extends the drain electrode as a series gate and constructs a tunable barrier homojunction using an air gap, which can effectively reduce dark current. Additionally, the introduction of this barrier shortens the transport distance for Te photogenerated electrons near the bottom double electrodes, optimizes carrier transport and collection, and enhances the photoelectric response speed. The built Te-based SBPT demonstrated the 0.6 nA room temperature dark current and the ultrafast response speed of 7.9 µs, both of which surpass previously reported Te-based phototransistors. Moreover, the SBPT detector obtained a sharp edge image at short-wave infrared, and the edge rise rate is 94.26. The SBPT architecture demonstrates cross-material compatibility with diverse semiconductor systems, thereby establishing a proof-of-concept for ultralow-power and high-speed optoelectronic devices.