Optical properties of a Cr/4H-SiC photodetector in the spectral range from ultraviolet to extreme ultraviolet.

This work examines the electrical and radiometric characteristics of a photodiode based on a 4H-SiC semiconductor material with a semitransparent Cr Schottky barrier of about 7 nm thickness. The device had a photosensitive area 10 mm in diameter. The spectral responsivity was determined in the wavelength range from 40 nm to 400 nm, thus particularly extending the characterization into the vacuum- and extreme ultraviolet spectral ranges. The photodiode showed a maximum quantum efficiency of 50% at 253 nm with a relative uniformity of 4% in the photosensitivity over its surface. The linearity of the photoresponse was measured at wavelengths of 70 nm and 265 nm for incident radiant powers from 2 nW to 800 nW, and no significant deviation from linearity was found. Regarding its electrical characteristics, the photodiode showed less than 10-13 A dark current at a reverse voltage of 10 V.