4H-SiC Schottky photodiodes, with 25 μ m epitaxial layers, employing thin (20 nm) Ni 2 Si Schottky contacts, were investigated for high temperature photon counting X-ray spectroscopy. Important X-ray photodiode detector parameters were extracted from electrical characterization within the temperature range 160° C to 0° C. The devices were found to be fully depleted at an applied electric field of 20 kV/cm; a leakage current density of 33 nA cm-2±1 nA cm− 2 at 160° C, was measured for one of the devices. The detectors were subsequently connected to low-noise photon counting readout electronics and investigated for their spectral performance at temperatures up to 100° C. With the charge-sensitive preamplifier operated at the same temperature as the detector the best energy resolution (Full Width at Half Maximum at 5.9 keV) obtained decreased from 2.20 keV±0.04 keV (120 e− rms±2 e− rms) at 100∘ …