Soft X-ray detection and photon counting spectroscopy with commercial 4H-SiC Schottky photodiodes

The results of electrical characterisation and X-ray detection measurements of two different active area (0.06 mm² and 0.5 mm²) commercial 4H-SiC Schottky photodiodes at room temperature are reported. The devices exhibited low dark currents (less than 10 pA) even at a high electric field strengths (403 kV/cm for 0.06 mm² diodes; 227 kV/cm for 0.5 mm² diodes). The results of the X-ray measurements indicate that the diodes can be used as photon counting spectroscopic X-ray detectors with modest energy resolutions: FWHM at 5.9 keV of 1.8 keV and 3.3 keV, for the 0.06 mm² and 0.5 mm² devices, respectively. Noise analysis of the photodiodes coupled to a custom low noise charge sensitive preamplifier is also presented.