  Tunable photovoltaic photodetectors are of significant relevance in the
fields of programmable and neuromorphic optoelectronics. However, their
widespread adoption is hindered by intricate architectural design and energy
consumption challenges. This study employs a nonvolatile MoTe2/hBN/graphene
semi-floating photodetector to address these issues. Programed with pulsed gate
voltage, the MoTe2 channel can be reconfigured from an n+-n to a p-n
homojunction, and the photocurrent transition changes from negative to positive
values. Scanning photocurrent mapping reveals that the negative and positive
photocurrents are attributed to Schottky junction and p-n homojunction,
respectively. In the p-n configuration, the device demonstrates self-driven,
linear, rapid response (~3 ms), and broadband sensitivity (from 405 to 1500 nm)
for photodetection, with typical performances of responsivity at ~0.5 A/W and
detectivity ~1.6*10^12 Jones under 635 nm illumination. These outstanding
photodetection capabilities emphasize the potential of the semi-floating
photodetector as a pioneering approach for advancing logical and nonvolatile
optoelectronics.
