  We report the first clear observation of interfacial superconductivity on top
of FeTe(FT) covered by one quintuple-layer Bi$_2$Te$_3$(BT) forming
van-der-Waals heterojunction. Both transport and scanning tunneling
spectroscopy measurements confirm the occurrence of superconductivity at a
transition temperature T$_c$ = 13~K, when a single-quintuple-layer BT is
deposited on the non-superconducting FT surface. The superconductivity gap
decays exponentially with the thickness of BT, suggesting it occurs at the
BT-FT interface and the proximity length is above 5-6~nm. We also measure the
work function's dependence on the thickness of BT, implying a charge transfer
may occur at the BT/FT interface to introduce hole doping into the FT layer,
which may serve as a possible candidate for the superconducting mechanism. Our
BT/FT heterojunction provides a clean system to study the unconventional
interfacial superconductivity.
