Diamond UV photoconductors: Defect passivation for high speed operation

Deep UV visible blind photoconductors fabricated on polycrystalline CVD diamond using inter-digitated structures have shown promising characteristics. The as-grown material device performance is insufficient for many applications; a particularly demanding example is the monitoring of high power excimer lasers operating in the UV which ideally requires visible-blind, radiation hard fast UV detectors. However, post-growth treatments can strongly modify the performance and in this paper we show that sequentially applied treatments can progressively change both the gain and speed of these devices. We have used charge sensitive deep level transient spectroscopy (Q-DLTS) to study the effect of these treatments on the defect structure of our CVD material. For the first time, we report the successful operation of a diamond photoconductive device at more than I kHz at 193nm, a common excimer laser wavelength and maximum operational repetition rate.