High resolution alpha particle detection using 4H-SiC epitaxial layers: Fabrication, characterization, and noise analysis

In this article we report the fabrication and characterization of large area, room-temperature operable and very high resolution Schottky barrier detectors for alpha particles using 20 μm thick n-type 4H-SiC epitaxial layers. Schottky barriers were fabricated by depositing circular nickel contacts of ~11 mm2 area on the 4H-SiC epitaxial layers. Room temperature current-voltage measurements revealed very high Schottky barrier height of 1.6 eV and extremely low leakage current of 3.5 pA at an operating reverse bias of −90 V. We also report an energy resolution of 0.29%, which is the best resolution obtained so far for uncollimated 5.48 MeV alpha particles in 4H-SiC epitaxial detectors with such a large area. Very low micropipe density (<1 cm−2) and low effective doping concentration (2.4×1014 cm−3) in the epilayer helped to achieve a high resolution even with the large detector area and a broad source. A diffusion length of ~18.6 μm for holes has been determined in these detectors following a calculation based on a drift-diffusion model. A noise analysis in terms of equivalent noise charge revealed that the white series noise due to the detector capacitance has substantial effect on their spectroscopic performance.