Radiation effect on pn-SiC diode as a detector

We studied radiation tolerance of pn junction 6H-SiC (silicon carbide) diodes on electrical properties and detector performance for alpha particles. Three pn-SiC diodes were irradiated with gamma-rays at doses (60Co source) up to 2.5 MGy and two diodes were irradiated with beta-rays (2 MeV) at fluences up to 1×1015 electrons/cm2. The ideality factors η, which are estimated from current-voltage (I-V) characteristics of diodes, were around 2.0 for all diodes, and no significant change in η was observed after both gamma and beta irradiations. The leakage currents increase with gamma doses up to range of 0.4-1.5 MGy and decrease with gamma doses above 1.5 MGy. For beta-rays, a little increase in leakage current was observed due to irradiation. The depletion layer width W was estimated from capacitance-voltage (C-V) characteristics of diodes. The W at several reverse bias voltage increases with increasing both gamma doses and beta fluences. The detector performance was examined by using alpha particles of two different energies, 4.3 and 1.8 MeV.For 1.8 MeV alpha particles, a charge collection efficiency, CCE, of 100% were demonstrated at reverse biases above 20 V, even after the irradiation at gamma doses up to 2.5 MGy.