Photoconductivity and internal photoemission in semiconducting diamond

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Abstract
The photoconductivity response spectrum of semiconducting natural diamond was measured over the range 0.5-6 eV. With silver-paint electrodes it exhibited peaks at 2, 3.3, 4.3, 5.1, and 5.6 eV. The 2-eV peak did not appear when the silver-paint electrodes were replaced by water electrodes. This peak was found to result from internal photoemission of holes from the metal electrode into the diamond. This conclusion was supported by previous results on tunnel spectroscopy, which fitted the photoconductivity spectrum except for the 2-eV peak. The interface barrier between the silver-paint electrode and the diamond was found to be 1.05 eV and the same value was obtained with evaporated silver or gold electrodes. With silver-paint electrodes the interface barrier could be reduced by "forming," i.e., by passing short pulses of high accurrents through the system.
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