High performance photodetector based on WSe2 p-n homojunction induced by the electron doping from Bi2O2Se

Compared with heterostructure engineering, which not only requires a complex alignment process but also inevitably introduces defects in the material preparation processes, the homojunction design advantages a clean interface that is beneficial to the device performance. In this work, in order to realize a 2D material-based p-n junction with a clean interface, a transverse WSe2 homojunction is constructed using the n-type Bi2O2Se placed beneath part of the WSe2 as the electron donor. The contact with Bi2O2Se induces an n-type region in the primarily p-type WSe2, creating a p-n junction with the neighboring pristine region. Moreover, because the carrier concentration in Bi2O2Se is large enough to block the back-gate voltage for the doped region in WSe2, the device can be converted between p-n and "quasi-n-p" (the undoped region has a higher Fermi level than the doped region) junction by gate voltage regulation. The device shows an excellent photoelectric performance in the visible region, with a high commutation ratio (105), high responsiveness (1.2 x 104 A/W), and fast response speed (rise and decay times of 230 mu s and 250 mu s). Therefore, doping with other materials as donor or acceptor is a promising and efficient method, which has broad prospects in future electronic and optoelectronic applications.