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.