  In this work, we demonstrate the suitability of Reconfigurable Ferroelectric
Field-Effect- Transistors (Re-FeFET) for designing non-volatile reconfigurable
logic-in-memory circuits with multifunctional capabilities. Modulation of the
energy landscape within a homojunction of a 2D tungsten diselenide (WSe$_2$)
layer is achieved by independently controlling two split-gate electrodes made
of a ferroelectric 2D copper indium thiophosphate (CuInP$_2$S$_6$) layer.
Controlling the state encoded in the Program Gate enables switching between p,
n and ambipolar FeFET operating modes. The transistors exhibit on-off ratios
exceeding 10$^6$ and hysteresis windows of up to 10 V width. The homojunction
can change from ohmic-like to diode behavior, with a large rectification ratio
of 10$^4$. When programmed in the diode mode, the large built-in p-n junction
electric field enables efficient separation of photogenerated carriers, making
the device attractive for energy harvesting applications. The implementation of
the Re-FeFET for reconfigurable logic functions shows how a circuit can be
reconfigured to emulate either polymorphic ferroelectric NAND/AND
logic-in-memory or electronic XNOR logic with long retention time exceeding
10$^4$ seconds. We also illustrate how a circuit design made of just two
Re-FeFETs exhibits high logic expressivity with reconfigurability at runtime to
implement several key non-volatile 2-input logic functions. Moreover, the
Re-FeFET circuit demonstrates remarkable compactness, with an up to 80%
reduction in transistor count compared to standard CMOS design. The 2D van de
Waals Re-FeFET devices therefore exhibit groundbreaking potential for both
More-than-Moore and beyond-Moore future of electronics, in particular for an
energy-efficient implementation of in-memory computing and machine learning
hardware, due to their multifunctionality and design compactness.
