Optical control of ferroelectric switching and multifunctional devices based on van der Waals ferroelectric semiconductors.

Indium Selenide (In2Se3) is a newly emerged van der Waals (vdW) ferroelectric material, which unlike traditional insulating ferroelectric materials, is a semiconductor with a bandgap of about 1.36 eV. Ferroelectric diodes and transistors based on In2Se3 have been demonstrated. However, the interplay between light and electric polarization in In2Se3 has not been explored. In this paper, we found that the polarization in In2Se3 can be programmed by optical stimuli, due to its semiconducting nature, where the photo generated carriers in In2Se3 can alter the screening field and lead to polarization reversal. Utilizing these unique properties of In2Se3, we demonstrated a new type of multifunctional device based on 2D heterostructures, which can concurrently serve as a logic gate, photodetector, electronic memory and photonic memory. This dual electrical and optical operation of the memories can simplify the device architecture and offer additional functionalities, such as ultrafast optical erase of large memory arrays. In addition, we show that dual-gate structure can address the partial switching problem commonly observed in In2Se3 ferroelectric transistors, as the two gates can enhance the vertical electric field and facilitate the polarization switching in the semiconducting In2Se3. These discovered effects are of general nature and should be observable in any ferroelectric semiconductor. These findings deepen the understanding of polarization switching and light-polarization interaction in semiconducting ferroelectric materials and open up their applications in multifunctional electronic and photonic devices.