A method was proposed for the determination of the state of an impurity (donor, acceptor, deep level) in a semiconductor. In order to demonstrate this method, B was diffused into type-Ia natural diamonds under a direct-current electric field. It was found that the B concentrations and diffusion profiles were affected by the applied field. The B diffused as a negative ion, since it was an acceptor that was shallow enough to be partially ionized at the diffusion temperature. The drift velocity of B ions at the diffusion temperature was also estimated. The diffusion of Li and O from a Li2CO3 source, in chemical vapor deposited diamond films, was performed under bias at 1000C in an Ar atmosphere. After diffusion, the concentrations of Li, O, and H in the films were found to be of the order of 3 x 1019 to 4 x 1019/cm3. No dependence of these concentrations upon the applied bias was observed. It was found that the diffusion of Li occurred mainly via grain boundaries. It was suggested that this explained why it did not depend upon the applied voltage. It was noted that F was present as an impurity in the dopant source. Its concentration in the films was of the order of 1017 to 2 x 1017/cm3, and depended upon the applied bias. This indicated that the F could form a shallow level in the diamond band gap.

G.Popovici, T.Sung, S.Khasawinah, M.A.Prelas, R.G.Wilson: Journal of Applied Physics, 1995, 77[11], 5625-9