Deep Levels in CVD Diamond and Their Influence on the Electronic Properties of Diamond-Based Radiation Sensors

Deep levels in undoped chemical vapor deposited (CVD) diamond films have been characterized by thermally stimulated current spectroscopy (TSC) in the range of 300–650 K. The TSC results have been tentatively correlated to the performance of the samples as on-line dosimeters and particle detectors. The TSC signal is dominated by a set of deep levels with an activation energy in the range of 1.0–1.4 eV. The trapping activity of these levels, which can be related to grain boundaries, strongly influences the detector performance at room temperature. After neutron irradiation up to the fluence of 2 × 1015 n/cm2 the amplitude of the TSC signal decreases of about one order of magnitude, the pumping effect becomes significantly less pronounced and the charge collection efficiency decreases of about 30%. Thus, the radiation-induced removal of these deep levels must be accompanied by the creation of other traps, probably vacancy-related and not visible by TSC in this temperature range, which have little effect on the dynamic response of the device but can affect the charge collection efficiency.