Proton Irradiation of Ultraviolet 4H-SiC Single Photon Avalanche Diodes

The effects of proton irradiation on ultraviolet 4H-SiC single photon avalanche photodiodes (SPADs) are investigated for the first time. The SPADs, grown by chemical vapor deposition, were designed for operation in the ultraviolet having dark count rates (DCR) of about 30 kHz and single photon detection efficiency (SPDE) of 4.89%. The SPADs were irradiated with 2 MeV protons to a fluence of 10¹² cm^-2. After irradiation, the avalanche breakdown voltage shifted downward 0.6 V from 113 V and the I-V characteristics show forward voltage (<; 1.9 V) generation-recombination currents 2 to 3 times higher than before irradiation. Single photon counting measurements at -114.2 V show lower voltage pulse height and a higher DCR at low threshold voltage, probably due to generation-recombination centers created in the band gap after irradiation. Yet, with the threshold voltage ranging from 23 to 26 mV, the 4H-SiC SPAD still showed low DCR (<; 54 kHz) and a reasonably high SPDE (>; 1%) after irradiation. The devices were demonstrated to show proton radiation tolerance for geosynchronous space applications.