Drift-diffusion model of self-biased 4H-SiC Schottky photodiodes for violet–ultraviolet emitting scintillator readout

4H-SiC is identified as a wide-bandgap semiconductor material for light readout from high speed, ultraviolet (UV) emitting scintillating materials that can operate in harsh environments, at high temperatures, and at zero applied bias. In this study, we have applied a numerical model based on drift-diffusion to evaluate the photo-response of Schottky photodiodes to radiation produced scintillation light in LaBr3:Ce (380 nm), LaCl3:Ce (350 nm), LuAG:Pr (310), and YAP:Pr (245 nm) on low-doped n-type 4H-SiC Schottky photodiodes with 50 μm active layers operating at zero bias. To investigate the impact of slow acting diffusion currents on charge collection and timing resolution, simulations were performed at various trapping rates functionalized based on the local electrostatic potentials. From these simulations, it was found that while charge collection of near-UV emitting LaBr3:Ce and LaCl3:Ce light is significantly improved by diffusion from the neutral region, their diffusion currents can extend the necessary charge collection time from their nanosecond decay times to several microseconds. LuAG:Pr and YAP:Pr—which absorb light closer to the interface—were far less sensitive to bulk trapping losses and demonstrated superior timing resolutions but can be severely impacted by majority carrier surface recombination at the metal–semiconductor interface. Simulations on p-type active layers demonstrated shorter diffusion tails than n-type, which could improve timing resolution by an order of magnitude for near-UV wavelengths even in self-biased mode. However, high majority carrier surface recombination rates present a significant bottleneck for the practical application of p-type materials even with longer wavelength emitting scintillators.