  Previous investigations of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ mainly focused on the
direct competition between superconductivity and charge density wave (CDW).
However, the superconductivity itself, although has been prominently enhanced
by isovalent Se substitution, has not been adequately investigated. Here, we
performed a detailed electrical transport measurement down to 0.1 K on a series
of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ single crystals. A systematic fitting of the
temperature-dependent resistance demonstrates that the decreased Debye
temperatures ($\Theta_{D}$) and higher electron-phonon coupling constants
($\lambda_{e-p}$) at the optimal Se doping content raise the superconducting
transition temperature ($T_c$). Additionally, we discovered that the
incorporation of Se diminishes the degree of anisotropy of the
superconductivity in the highly layered structure. More prominently, a
comprehensive analysis of the vortex liquid phase region reveals that the
optimally doped sample deviates from the canonical 2D Tinkham prediction but
favors a linear trend with the variation of the external magnetic field. These
findings emphasize the importance of interlayer interaction in this segregated
superconducting-Mott-insulating system.
