Generation of electrical damage in n-GaN films following treatment in a CF4plasma

We have investigated the generation of electrical damage in n-GaN films following treatment in a CF4 plasma, employing capacitance–voltage and steady-state photocapacitance spectroscopy techniques. The effective carrier concentration at depths of 50–150 nm from the GaN surface decreases, probably owing to Ga vacancies (VGa) diffusing into the bulk after being introduced at the surface by ion bombardment. These vacancies consequently form acceptor-type hydrogenated VGa with optical onsets at ~1.79 and ~3.23 eV below the conduction band. In particular, the dominant 3.23 eV level is most likely attributed to (VGa–H2)− species, because the VGa concentration at depth is very low.