SURFACE TREATMENT OF SEMICONDUCTOR SUBSTRATE USING FREE RADICAL STATE FLUORINE PARTICLES

A substrate having a buffer layer and a barrier layer is formed. The buffer and barrier layers have different bandgaps such that an electrically conductive channel comprising a two-dimensional charge carrier gas arises at an interface between the buffer and barrier layers due to piezoelectric effects. The substrate is placed in a fluorine containing gas mixture that includes free radical state fluorine particles and is substantially devoid of ionic state fluorine particles. A first lateral surface section of the substrate is exposed to the gas mixture such that the free radical state fluorine particles contact the first lateral surface section without penetrating the substrate. A semiconductor device that incorporates first lateral surface section in the structure of the device is formed in the substrate.