Charge-Based Deep Level Transient Spectroscopy of Defects in Electron-Irradiated and Annealed CVD Diamonds

Electrically active defects in undoped and moderately boron-doped microwave plasma CVD diamond films subjected to electron-irradiation and/or vacuum annealing to high, up to 1625 °C, temperatures were studied with Charge-based Deep Level Transient Spectroscopy. Concentration, activation energy EA, and capture cross-section of native and boron-related defects are determined. The undoped samples before the treatments displayed the acceptor defects with a continuous energy spectrum, while the B-doped samples showed two discrete levels with EA of 0.37 and 0.25 eV. The electron irradiation (2 MeV, dose 5 x 1018 cm-2) changes the parameters of boron-induced levels, reduces the concentration of the defects with the continuous energy spectrum, and strongly, by four orders of magnitude, reduces electrical conductivity. After annealing only one B-related level with EA = 0.37 eV (boron in substitutional position) remains, but simultaneously an increase in abundance of acceptor defects with low activation energy was observed.