Development of a Silicon Carbide Schottky Diode Detector for Use in Determining Actinide Inventories based on Alpha Particle Spectroscopy

Deployment of Generation IV nuclear power will require novel materials as well as new techniques for monitoring plant functions. Reprocessing of spent nuclear fuel will play a large role in the future generations of reactors. It would be useful if real-time measurements of actinide concentrations during reprocessing could be achieved through alpha spectroscopy. Devices built upon silicon carbide offer the best hope of surviving the harsh chemical, and high radiation and high temperature environments associated with reprocessing.

In this project 4H-SiC alpha particle detectors were built and tested up to high temperature in order to simulate some of the conditions a detector might encounter in the pyroprocessing environment. The silicon carbide used in this project had a low-doped (5x10¹⁴ atoms/cm³ of nitrogen) 21 micron thick epitaxial layer grown on top of a 300 micron thick bulk substrate with a nitrogen doping concentration of 1x10¹⁸ atoms/cm³. 100 nm of nickel, 10 nm of titanium, and 10 nm of gold were deposited, in that order, on the epitaxial side and annealed to form a Schottky contact. An ohmic contact was formed by annealing from 100 nm of nickel deposited on the substrate and annealed. The devices were characterized through IV curve measurements and then exposed to Am-241 alpha particles and high temperature while in vacuum.

Mixed results show that these detectors can operate up to 100 degrees Celsius with very little change in peak location, full width half max (FWHM) and energy resolution. The FWHM remained below 100 keV, while the energy resolution was below 1.57%. At 150 degrees Celsius, the FWHM remained below 190 keV while the energy resolution was below 3.46%. Temperatures above 150 degrees Celsius pose significant problems to the current design as the alpha peak moves to lower channels and broadens to have a full width half max between 300 and 500 keV. The current state of literature on SiC Schottky diode detectors shows that no other Schottky diode detectors have been tested up to higher temperatures with a better resolution.