  Although van der Waals layered transition metal dichalcogenides from
transient absorption spectroscopy have successfully demonstrated an ideal
carrier multiplication (CM) performance with an onset of nearly
2Eg,interpretation of the CM effect from the optical approach remains
unresolved owing to the complexity of many-body electron-hole pairs. We
demonstrate the CM effect through simple photocurrent measurements by
fabricating the dual-gate P-N junction of a MoTe2 film on a transparent
substrate. Electrons and holes were efficiently extracted by eliminating the
Schottky barriers in the metal contact and minimizing multiple reflections. The
photocurrent was elevated proportionately to the excitation energy. The boosted
quantum efficiency confirms the multiple electron-hole pair generation of >2Eg,
consistent with CM results from an optical approach, pushing the solar cell
efficiency beyond the Shockley-Queisser limit.
