Defect Engineering in β‐Bi ₂ SeO ₅ /Bi ₂ O ₂ Se Heterostructures for High‐Resolution Phototransistor Arrays

Abstract

Abstract Analogous to the pivotal SiO 2 /Si junction in modern electronics, the β‐Bi 2 SeO 5 /Bi 2 O 2 Se architecture has been demonstrated to enhance the performance of electronic devices. However, its potential to improve the optoelectronic properties of Bi 2 O 2 Se, such as responsivity and detectivity, remains unexplored. The photodetection performance of Bi 2 O 2 Se is primarily limited by intrinsic selenium vacancies at its surface, which lead to low photocurrent and instability. To address this, a defect‐engineered β‐Bi 2 SeO 5 /Bi 2 O 2 Se heterojunction is constructed with an atomically sharp interface via a developed UV‐assisted oxidation strategy. This heterostructure successfully suppresses surface vacancies while enabling dual functionality—surface passivation and photoactive charge separation, resulting in substantially enhanced optoelectronic performance. First‐principles calculations confirm a stable type‐II band alignment with interfacial transitions enabling efficient carrier dissociation. The visible‐near‐infrared transparency and high‐ k of β‐Bi 2 SeO 5 further enable top‐gated phototransistors with dynamically tunable photoresponse, achieving the largely improved metrics of responsivity (1.2 × 10 4 A W −1 ), detectivity (1.5 × 10 13 Jones), and on/off ratio (2.3 × 10 6 ). Additionally, by using thermal scanning probe lithography, a high‐resolution (pixel pitch = 6.5 µm) β‐Bi 2 SeO 5 /Bi 2 O 2 Se phototransistor array is fabricated and its imaging capabilities are demonstrated. The results establish an effective defect‐engineered strategy with in situ large‐area growth capability of β‐Bi 2 SeO 5 and high‐resolution device patterning, making β‐Bi 2 SeO 5 /Bi 2 O 2 Se a promising photoresponsive platform for advanced optoelectronic devices.