Nearly exponential dependence on photon energy of the photoconductivity of electron irradiated semiconducting diamond

The photoconductivity (PC) of electron irradiated semiconducting diamond was examined over the energy range 1 to 4 eV and over the temperature range 76 to 500 K. The PC response spectra exhibited a strong drop below 3 eV. In one sample this drop was by a factor of nearly 104 from 3 to 2 eV. In the range of the Ar laser lines (2.41 to 2.73 eV) the PC depended nearly exponentially on photon energy. A mechanism involving competition for the absorption of the exciting light between the non-photoconductive GR1 system and the photoconductive UV absorption band gives a good account of the experimental results. This includes the photon energy dependence of the PC and its thermal dependence. The proposed mechanism is further supported by the absence of the drop in PC near 2.5 eV in a lightly colored electron irradiated diamond. (author)