Research On The Radiation Hardness Feature Of SiC SBD And MESFET

The radiation effect of the Ni/4H-SiC SBD and MESFET were studied in this thesis. The influence of the traps induced by irradiation on their characteristics were focused. In the SBD's simulation, traps in the material make the forward current and reverse current decreased. In the MESFET's simulation, we found that it can withstand more traps in the material induced by irradiation due to the higher impurity concentration in the channel.The Ni/4H-SiC Schottky barrier diodes (SBDs) and TLM (Transfer Length Method) test patterns of Ni/4H-SiC ohmic contacts were fabricated, and irradiated with1Mev electrons up to a dose of 3.43×l0¹⁴e/cm^-2.After radiation, the forward currents of the SBDs at 2v decreased by about 50%, and the reverse currents at -200v increased by less than 30%. Schottky barrier height (φ_B) of the Ni/4H-SiC SBD increased from 1.20ev to 1.21ev under Ov irradiation bias, and decreased from 1.25ev to 1.19ev under -30v irradiation bias. The degradation ofφ_B could be explained by the variation of interface states of Schottky contacts. The on-state resistance (Rs) and the reverse current increased with the dose, which could be ascribed to the radiation defects in bulk material. The specific contact resistance (ρ_c) of the Ni/SiC ohmic contact increased from 5.11×10^-5Ωcm² to 2.97×l0^-4Ωcm².The Ni/4H-SiC Schottky barrier diodes(SBDs) were irradiated with the ⁶⁰Co gamma-ray source to the accumulated dose of 1Mrad(Si).0v and -30v bias voltages were applied to the SBDs during irradiation. After 1Mrad(Si) radiation, Schottky barrier height and ideality factor of the Ni/4H-SiC SBDs under different bias voltage basicly remain the same values, and minority carrier lifetime of the epitaxial layer also has nodegradation.The reverse current decreases after radiation, which can be explained by the negative surface charge increase. The results show radiation bias voltage has little influence of gamma-ray on the Ni/4H-SiC SBD.Through testing and simulation data, we found after radiation with 1MeV electrons up to a dose of 3.43×10¹⁴e/cm^-2,the Schottky barrier height changed slightly and recovered with annealing at room temperature for a week. But Rs didn't recover after a week.1Mrad(Si) gamma-ray radiation hardly change the Ni/4H-SiC SBD's characters. These data show that 4H-SiC SBDs have excellent capability of radiation hardness.