Relaxations of the below-gap photo-current, following ultra-violet illumination, were studied in polycrystalline chemical vapor deposited material at various wavelengths (300 to 657nm). The high-temperature peak which was usually observed in thermally stimulated current curves was shown to be closely related to the below-gap photo-current relaxation. The results suggested that optical de-trapping of carriers previously trapped during ultra-violet illumination occurred during below-gap photo-current relaxation; with an onset at photon energies of 2.3 to 2.5eV. These were much greater than the values of activation energy which were attributed to the defect level that was responsible for the thermally stimulated current peak.

Study of Deep Defects in Polycrystalline CVD Diamond from Thermally Stimulated Current and Below-Gap Photocurrent Experiments. J.Alvarez, J.P.Kleider, P.Bergonzo, D.Tromson, E.Snidero, C.Mer: Diamond and Related Materials, 2003, 12[3-7], 546-9