The effect of screening of the coulomb interaction between two layers of two-dimensional electrons, such as in graphene, by a highly doped semiconducting substrate is investigated. We employ the random-phase approximation to calculate the dispersion equation of this hybrid structure in order to determine the plasmon excitation spectrum. When an electric current is passed through a layer, the low-frequency plasmons in the layer may bifurcate into separate streams due to the current-driving effect. At a critical wave vector, determined by the separation between layers and their distance from the surface, their phase velocities may be in opposite directions and a surface plasmon instability leads to the emission of radiation. Applications to detectors and other electromagnetic devices exploiting nano-plasmonics are discussed.