Characterization of deep defects in boron-doped CVD diamond films using transient photocapacitance method

We have developed a highly-sensitive transient photocapacitance measurement (TPM) system for deep defects in wide bandgap materials, and applied it to characterize the boron-doped diamond films grown on a high-pressure/high-temperature-synthesized Ib diamond substrate using high-power-density microwave-plasma chemical vapor deposition method. The developed TPM system has both a low detection limit of less than 0.5 fF for changes in the photocapacitance and a low measurement temperature drift of less than 0.03 K in 12 h. By using the TPM system, we have successfully found an acceptor-type defect around 1.2 eV above the valence-band maximum for the B-doped diamond film with a considerably high crystalline quality that had some strong exciton emission peaks in the cathodoluminescence spectra taken at ≈80 K. The photoionization cross section and the defect density estimated for the observed defect were 3.1×10-15 cm2 and 2.8×1016 cm−3, respectively.