Fourier-Transform Photocurrent Spectroscopy of Defects in CVD Diamond Layers

Fourier-transform photocurrent spectroscopy has been used for the first time to study defects in nominally undoped CVD diamond layers. The hydrogenated surface of diamond ("as grown" or post-hydrogenated) has been annealed in air and changes in surface conductivity and photoconductivity have been monitored as a function of temperature and time. The reduction of surface conductivity with annealing led to an enhancement of photosensitivity and enabled us to study the spectral distribution of the photoionization cross section of shallow and deep defects in the gap over several orders of magnitude in the temperature range of 77-400 K. The photo-Hall effect was used for the determination of the sign of photogenerated carriers. An anomalous temperature dependence of the acceptor defect level was detected. A residual boron contamination was observed in one layer.