  Two-dimensional (2D) intrinsic ferromagnetic semiconductors are expected to
stand out in the spintronic field. Recently, the monolayer VI$_{3}$ has been
experimentally synthesized but the weak ferromagnetism and low Curie
temperature ($T_C$) limit its potential application. Here we report that the
Janus structure can elevate the $T_C$ to 240 K. And it is discussed that the
reason for high $T_C$ in Janus structure originates from the lower virtual
exchange gap between $t_{2g}$ and $e_{g}$ states of nearest-neighbor V atoms.
Besides, $T_C$ can be further substantially enhanced by tensile strain due to
the increasing ferromagnetism driven by rapidly quenched direct exchange
interaction. Our work supports a feasible approach to enhance Curie temperature
of monolayer VI$_{3}$ and unveils novel stable intrinsic FM semiconductors for
realistic applications in spintronics.
