The dynamic interplay between light and electric field control of charge states lies at the heart of developing multifunctional optoelectronic devices. While persistent photoconductivity (PPC) and gate voltage (VG)-induced electron trapping are well-known phenomena in oxide heterostructures, their mutual coupling remains poorly explored. Here, we report that the non-equilibrium state established by PPC can effectively modulate the efficacy of VG-induced electron trapping in a SrTiO3/AlOx heterostructure. After the cessation of light illumination, the decay of PPC shows a slow relaxation with time constant τl = 9 h at 4 K, which originates from the re-trapping of photoexcited carriers into deep level states. In contrast, the electron trapping induced by the application of VG is governed by shallow states and exhibits much faster dynamics (τ ∼ 100 s). Crucially, we discover that the strength of VG-induced trapping is not constant but is dynamically modulated by the PPC relaxation process. The trapping amplitude is strongly amplified after illumination and recovers only after the deep-level states are substantially refilled, precisely following the PPC relaxation. Furthermore, the electron trapping effect diminishes with increasing temperature and vanishes near the ferroelastic phase transition of SrTiO3 (∼110 K), confirming that ferroelastic twin walls and associated oxygen vacancy clusters are the physical origin of the traps. Our findings reveal a novel optical gating mechanism that may inspire future designs of optically programmable oxide electronics.
Luo et al. (Mon,) studied this question.
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