Mechanism of photoconductivity in intrinsic epitaxial CVD diamond studies by photocurrent spectroscopy and photocurrent decay measurements

Abstract

We report experimental results on photocurrent spectra and the transient decay of photocurrent in intrinsic CVD diamond films grown homoepitaxially on natural, (100) oriented, single crystal type Ila diamond substrates. The detectors fabricated from these layers were developed in the frame of the LYRA-project (the LYman-alpha RAdiometer onboard the European satellite PROBA-2) and will be used in space for UV solar monitoring. The typical photosensitivity is about 10−2 A/W at 200 nm and 10−6 A/W at 300 nm; the typical response time wel below 0.1 ms. The enhance in photosensitivity, related to defects in CVD diamond layer and accompanied by long, non-exponential tails in photocurrent transients (persistent photocurrent), is observed in some detectors. The enhancement in photosensitivity also correlates with a long effective lifetime of photo-excited carriers. New effects at about 3.8 eV and another at about 4.3 eV are observed in the photocurrent spectrum of the sample with enhanced photosensitivity.