Study of deep defects in polycrystalline CVD diamond from thermally stimulated current and below-gap photocurrent experiments

We study the relaxations of the below-gap photocurrent (BGPC) following UV illumination in polycrystalline chemical vapour deposition diamond at different wavelengths (300 nm less than or equal to lambda less than or equal to 657 nm) and the implication on subsequent thermally stimulated current (TSC) experiments. The high temperature peak usually observed in TSC curves is shown to be intimately related to the BGPC relaxation. Results suggest that optical de-trapping of carriers previously trapped during UV illumination occurs during BGPC relaxation, with an onset at 2.3-2.5 eV photon energies. This is much more than the values of activation energies attributed to the defect level responsible for the TSC peak. Results are discussed in the framework of existing models of defect distributions. (C) 2003 Elsevier Science B.V All rights reserved.