Effects of very high neutron fluence irradiation on p(+)n junction 4H-SiC diodes

In this work we analyzed the radiation hardness of SiC p(+)n diodes after very high 1 MeV neutron fluence. The diode structure is based on a p(+) emitter ion implanted in n-type epilayer with thickness equal to 5 mu m and donor doping N-D = 3x 10(15) cm(-3). Before irradiation, the average leakage current density at 100 V reverse bias was of the order of 3 nA/cm(2). These devices were irradiated at four different fluence values, logarithmically distributed in the range 10(14)-10(16) (1 MeV) neutrons/cm(2). After irradiation the epilayer material became more resistive, as indicated by the reduction of the forward and reverse current density at a given voltage. In particular, after a neutron fluence of I X 1014 n/cm(2) the epilayer active doping concentration decreased to 1.5X10(15) cm(-3). After irradiation at 10(16) n/cm(2), i.e. the highest fluence value, the average leakage current density at 100 V reverse bias decreased to values of the order of 0.1 nA/cm(2). This very low noise even after very high fluence is very important to obtain a high signal to noise ratio even at room temperature.