Ultrasensitive Self-Powered Deep-Ultraviolet Photodetector Based on In Situ Epitaxial Ga₂O₃/Bi₂Se₃ Heterojunction

The Ga
₂
O
₃
-based deep-ultraviolet photodetectors (DUV PDs) possess great potential due to the suitable bandgap and desired stability. However, the compulsive external bias and the undesired response speed severely limit its large-scale implementations. Herein, we report a highly efficient self-powered Ga
₂
O
₃
/Bi
₂
Se
₃
heterojunction PD, fabricated through an
in situ
epitaxial deposition process. The Ga
₂
O
₃
and Bi
₂
Se
₃
films are found to present a van der Waals bonding with great orientation crystallinities. Under the self-powered mode, the device presents a stable and favorable photoresponsivity with an ultralow dark current of 3.12 pA and an excellent detectivity of
$6.23 \times 10^{{13}}$
Jones under 245-nm light illumination. Moreover, the device presents an ultrafast rise and decay response time of 0.6 and 1.2 ms, which achieves more than four orders of magnitude reduction compared to the Ga
₂
O
₃
photoconductor. Such excellent improvement can be attributed to the high-quality Ga
₂
O
₃
/Bi
₂
Se
₃
heterojunction and the high carrier mobility of Bi
₂
Se
₃
, which is beneficial for improving the separation and transfer efficiency of the electron–hole pairs. This work provides a new direction for developing the Ga
₂
O
₃
based DUV PD.