10–30 Å thick Si interface control layers (ICL) were deposited on GaAs epitaxial layers on GaAs substrates. These were then nitrided by exposure to an electron cyclotron resonance nitrogen plasma for varying times. The nitride thickness is shown to increase logarithmically with time. A model based on electron tunneling is proposed to explain the results. Capacitance–voltage measurements on resulting dielectric layers showed that, under optimal conditions, results adequate to fabrication of high-performance field-effect transistors are possible. The ICL thickness cannot be reduced to zero by nitridation because of damage to the underlying GaAs.