On Photocurrent (and EPR) Study of Defect Levels in CVD Diamond

Photocurrent spectroscopy is used for studying electronic defect states in the gap of optical-quality CVD diamond. The constant photocurrent method (CPM), allowing to measure the optical (photoionization) cross-section of defects, is applied on samples with a different surface treatment. The measured photoionization cross-section spectra are discussed and attributed to main defects in CVD diamond layers. A photoionization cross-section of a defect, with an onset at about 2.2 eV, is attributed to the single-substitutional nitrogen defect (EPR P1 resonance at g = 2.0024). This defect is denoted as D2. Additionally, a defect with an onset at about 1.2 eV is observed on “as-grown” samples or after additional hydrogen plasma treatment. This defect, denoted as D1, diminishes after oxidation of the diamond sample surface. The EPR g = 2.0028 resonance, which was also suggested to be H-related, is studied as a function of hydrogenation and oxidation.