Analysis of trapping-detrapping defects in high quality single crystal diamond films grown by chemical vapor deposition

The photoresponse of high quality single crystal diamond films homoepitaxially grown by Chemical Vapor Deposition (CVD) onto low cost diamond substrates has been studied. The time evolution electrical response to the excitation by 5 ns laser pulses at 215 nm closely reproduces the laser pulse shape. The single crystal diamond response is therefore much faster than the laser pulse duration. The output signal is also very stable and reproducible, without significant priming or memory effects. Single crystal diamond films can therefore be grown by CVD having enough high quality to be used as photodetectors. However, a minor slow component shows up in the charge-integrated sample response. A systematic speed up of this slow component when increasing the detector temperature from - 25 °C to + 50 °C demonstrates its thermally activated origin. The slow component is therefore attributed to detrapping effects from shallow trapping centres. A model of the charge transport mechanism in the presence of trapping-detrapping centres can be developed and the results can be compared to the experimental ones. The activation energy of the shallow defects is accordingly determined as Ea=0.4eV.