Gate tunable photodetection and imaging in WS2 phototransistors enabled by a lithium niobate functional substrate

Abstract

Heterogeneous integration with two-dimensional materials offers a promising route to address the photoelectric conversion challenges of lithium niobate (LiNbO3, LN). However, previous works have mostly relied on the weak spontaneous polarization of LN, which underutilizes the potential of ferroelectric polarization and lacks sufficient degrees of freedom for programmable control. In this work, we fabricate a LiNbO3/WS2 phototransistor via photolithography and van der Waals transfer, and back-gate voltage is employed to achieve programmable modulation of the photocurrent magnitude and polarity, which can be interpreted through a parallel-plate capacitor model combined with the pyroelectric effect. Moreover, the thin-film LN enables back-gate modulation while retaining the ferroelectric and pyroelectric functionalities of LN, allowing the photoresponse of the WS2 channel to be continuously regulated by the gate voltage, leading to exceptional programmable performance with Ilight/Idark ratio tunable from 26.6 to 66 437.82 and responsivity from 5.47 to 492.35 A/W, while photocurrent imaging further reveals that the back-gate bias continuously adjusts the trade-off between image brightness and contrast. This work establishes that functional polarized substrates can provide a new system-level control dimension for two-dimensional optoelectronic devices, paving the way for programmable detection, adaptive imaging, and task-oriented intelligent sensing.