Carrier trapping and release in CVD-diamond films

Transient photocurrent experiments were performed to investigate transport and trapping kinetics in highly oriented (HOD) and polycrystalline (PD) chemical vapour deposition-diamond films perpendicular and parallel to the growth direction. The results indicate better electronic properties in PD then in HOD and do not reveal any transport anisotropy in the HOD. Interactions with shallow bulk and grain boundary traps are detected in both PD and HOD. The main drift length is about 1 -2.6 mu m. Deeply trapped carriers generate a space charge electric field which was measured by d.c.-photoconductivity experiments in the short circuit mode. The relaxation of the space charge field lasts for several minutes at T=300 K. The decay is non-exponential and not thermally activated in the regime 300-700 K.