Optoelectronic devices based on ferroelectric 2D van der Waals heterostructures

The demand for decreasing dimensions of electronic devices has been growing since the invention of the first computer. The benefits of miniaturization are power consumption/heating reduction, operation speed, cost and portability. Two-dimensional (2D) materials have been drawing utterly strong attention since their discovery in 2004 by Andrey Geim and Konstantin Novolselov. The utilization objective stems from their outstanding properties such as one-atom thickness, impurity-free structures, dangling bonds-free interfaces, ultimately high Young’s modulus, immense thermal- and electroconductivity. There are mainly four categories of Van der Waals materials: graphene family, Xenes (borophene, phosphorene, etc.), transitional metal dichalcogenides – TMDC (In2Se3, MoS2, WSe2, MoTe, etc.), and 2D oxides (MnO2, PbO, etc.). The room-temperature stable ferroelectricity down to the monolayer thickness makes In2Se3 a perfect candidate for a novel low write-power, non-volatile memory, and cutting-edge electro-optical devices. Moreover, the intercoupling between in-plane (IP) and out-of-plane (OOP) polarization and the optical ferroelectric polarization switching introduces additional leverages for device manipulation.

Electrostatic tunability is an essential feature of 2D materials that comes from reduced thickness. It allows device doping with voltage bias, which makes it possible to develop a more resilient design and without compromising the charge carriers mobility. In the present research, we fabricate 2D optoelectronic devices based on 2D α‎-In2Se3 combined with TMDCs such as n-type MoS2 and ambipolar WSe2. We demonstrate configurable p-n junction using electrostatic doping. In addition, we characterize the photoresponse and the photovoltaic effects showing broadband efficient operation. Finally, the ferroelectric nature of In2Se3 enables the memorization of multibit electronic states, paving the way towards novel optical in-memory operation.