Bias-tunable persistent photoconductivity for photoelectric memory in van der Waals heterojunctions of black phosphorus/2D electron gas on SrTiO3

Persistent photoconductivity (PPC) describes the light-induced persistent enhancement of conductivity after turning off the light, which is tunable by a gating voltage. Here, we report a bias-tunable PPC in van der Waals heterojunctions of black phosphorus/2D electron gas (BP/2DEG) on SrTiO3. With a light pulse applied, the resistance of a BP/2DEG heterojunction decreases dramatically over five orders of magnitude. Such a low resistive state is maintained over 5 days without any sign of recovery. The application of the negative bias voltage can tune the device into a high resistive state. By combining the light and bias voltages, the device enables it to change into any resistance value, indicating a potential application for multi-bit photoelectric memory. Further study demonstrates that the BP/2DEG heterojunction can achieve both optical writing/electric erasing and electric writing/optical erasing. Our work paves the way to control the PPC through the bias voltage. Published under an exclusive license by AIP Publishing.