Comparison of diamond and silicon ultraviolet photodetectors

Measurements have been made on a commercially produced diamond detector, and on detectors made in-house, all based on polycrystalline chemical vapour deposited (CVD) diamond. The uniformity of response over the sensitive area of each detector has been mapped with 50 or 100 mu m resolution and the signal-to-noise ratios have been measured at 220 nm (which is near the peak of the response for the diamond detectors). We find huge variations in sensitivity as the position of the spot on the diamond detector is moved. In the most sensitive regions the photocurrent, with a bias of 0.3 V mu m(-1), can be much larger than that obtained from a silicon photodiode operated in the short-circuit mode; however, the signal-to-noise ratio and stability of the signal are superior for the silicon detector. All the diamond detectors respond to visible light to a certain extent, particularly after illumination with ultraviolet (UV) radiation, and the UV response is modified if the detector is simultaneously illuminated with visible light. These phenomena indicate the presence of trapping centres in the material. (C) 1999 Elsevier Science S.A. All rights reserved.