Remote phonon scattering in field-effect transistors with a high κ insulating layer

In this paper a remote phonon scattering of channel electrons in a field-effect transistor (FET) with a high dielectric constant ( κ ) insulator in between the gate and the channel is studied theoretically. The spectrum of phonons confined in the high κ layer and its modification by the gate screening is investigated. Only two phonon modes of five participate in the remote electron-phonon scattering. The gate suppresses one of the modes but increases scattering by the other. Numerical results for the channel mobility limited only by remote phonon scattering were obtained for a Si FET with a HfO 2 layer and a SiO 2 layer in between the channel and metallic gate. A surprising result is the reduction of the mobility compared to the case when the gate screening is absent. The dependence of the mobility on the widths of HfO 2 and interfacial SiO 2 layers on channel concentration and temperature was studied. The accuracy of the calculations based on the Boltzmann equation is discussed. Finally, a comparison of our results with available experimental data leads to the conclusion that the remote phonon scattering is not the dominating scattering mechanism.