In order to design a viable nanoplasmonic device it is essential to be able to control the excitation of plasmon polaritons using an external voltage bias. To achieve this we can employ the phenomenon of electron inelastic tunneling followed by photon excitation and a subsequent launch of the plasmon polariton. Unfortunately, this process suffers from low efficiency. In this paper, we propose the use of spherical Si and Au nanoantennas to increase the energy conversion from photon to plasmon. We show that size-governed Mie resonances of nanoantenna determine the spectral position of peak efficiency. The size of the nanoantenna also determines the efficiency value, which can reach up to 25%. This is an order of magnitude higher compared to the case without nanoantenna. An analysis of thermal stability proves that both types of nanoantennas can operate under high current rates at room temperature.