Doping of 6H–SiC pn structures by proton irradiation

The influence of proton irradiation on current–voltage characteristics, N d − N a values and parameters of deep centres in 6H–SiC pn structures grown by sublimation epitaxy has been studied. The irradiation was carried out with 8 MeV protons in the range of doses from 10 14 to 10 16 cm −2. Irradiation with a dose of 3.6 × 10 14 cm −2 leaves the voltage drop at high forward currents (10 A/cm 2) practically unchanged. For higher irradiation dose of 1.8 × 10 15 cm −2, the forward voltage drop and the degree of compensation in the samples increased ; partial annealing of the radiation defects and partial recovery of the electrical parameters occurred after annealing at T∼400–800 K. Irradiation with a dose of 5.4 × 10 15 cm −2 resulted in very high resistance in forward biased pn structures which remained high even after heating to 500°C. It is suggested that proton irradiation causes decreasing of the lifetime and formation of an i- or an additional p-layer.