We present a theoretical study of the plasmon excitation spectrum in a silicene-Q2DEG heterostructure, focusing on the role of finite temperature, bandgap parameters, interlayer separation, and quantum well width. By employing analytical derivations combined with numerical calculations, we identify two distinct plasmon branches: the optical and acoustic modes. The optical branch displays a characteristic \(\sqrt q\) -like dispersion and is highly sensitive to structural confinement and bandgap engineering, whereas the acoustic branch is quasi-linear in the long-wavelength limit and more robust, though it may be suppressed near the single-particle excitation boundary. We identify that reducing the interlayer spacing or the quantum well width enhances the plasmon frequencies by enhancing Coulomb coupling. An enhanced field-induced band gap significantly stiffens the optical plasmon branch, while the acoustic mode exhibits a significantly lower sensitivity on the bandgap parameter than the optical mode within the investigated range. At finite temperatures, the optical mode exhibits a nonmonotonic behavior, whereas the acoustic mode varies much less strongly with temperature than the optical branch. These results demonstrate the tunability of plasmons, especially for the optical mode, in heterostructures consisting of silicene.
