Extreme UV single crystal diamond Schottky photodiode in planar and transverse configuration

We report on the study of the performances of two extreme ultraviolet (EUV) photovoltaic single crystal diamond Schottky diodes based on metal/intrinsic/p-type diamond junction developed at the University of Rome “Tor Vergata” and having different contact geometries. One detector operates in transverse configuration with a semitransparent metallic contact evaporated on the intrinsic diamond surface, while the second one operates in planar configuration with an interdigitated contact structure on the growth surface of the intrinsic diamond layer. Both devices can work in an unbiased mode by using the built-in potential arising from the electrode–diamond interface and show excellent rectifying properties with a rectification ratio of about 108.The devices have been characterized in the EUV spectral region by using He–Ne DC gas discharge radiation source and a toroidal grating vacuum monochromator, with a 5 Å wavelength resolution. The extremely good signal-to-noise ratio, the reproducibility of the device response, the absence of persistent photoconductivity and undesirable pumping effects suggest the high quality of our CVD diamond for UV applications. The external quantum efficiency (EQE) as well as the responsivity have been measured in the spectral range from 20 to 120 nm and opposite behaviours for the two different geometries proposed have been observed.