Electrical damage investigation of n-GaN films treated by CF4 plasma

The generation behavior of damage introduced into n-GaN by CF 4 plasma treatments has been electrically investigated, employing capacitance-voltage (C-V) and steady-state photo-capacitance spectroscopy (SSPC) techniques. The plasma treatments tended to decrease the effective carrier concentration |N D -N A | in the deeper-lying regions up to ∼150nm from the GaN surface, probably due to the in-diffusion of introduced Gallium vacancy (V Ga ) under the UV exposure from the plasma and the resultant formation of acceptor-type hydrogenated V Ga (V Ga -H n complexes) with their optical onsets at ∼2.1, ∼2.8, and ∼3.25eV below the conduction band. In particular, in the case of CF 4 plasma treatments, shallow-acceptor type V Ga -H 3 defects (∼3.25eV level) are considered to be easily formed because of the amount of the in-diffused V Ga being very small except for the numerous F-terminated V Ga near the GaN surface.