Study of the effect of hydrogen on transport properties in chemical vapor deposited diamond films by Hall measurements

Abstract

Using Hall effect measurements, we have investigated carrier transport in a high-conductivity layer formed in the surface region of as-deposited homoepitaxial diamond films prepared by chemical vapor deposition. The results of undoped and B-doped films were compared to those obtained from an oxidized B-doped film. It is found that (1) the carrier (hole) density per unit area of both as-deposited films is 4–5 orders of magnitude larger than that of the oxidized B-doped film at 297 K and is nearly constant in the temperature range of 150–400 K, while that of the oxidized B-doped film shows a strong temperature dependence with an activation energy of 0.38 eV, and (2) the Hall mobility of both as-deposited films is 1–2 orders of magnitude smaller than that of the oxidized B-doped film at 297 K and increases with increasing temperature, while that of the oxidized B-doped film decreases. These results and the secondary ion mass spectroscopy analysis suggest that the high-conductivity layer formed in the as-deposited films originates from the incorporated hydrogen in the subsurface region.