High electron mobility achieved in n-channel 4H-SiC MOSFETs oxidized in the presence of nitrogen

摘要

Two types of nitrided n-4H-SiC MOSFETs have been investigated; the p-type 4H-SiC epilayer is either oxidized in the presence of N_2O or an N-/Al-co-implanted, surface-near layer is over-oxidized. The electrical parameters of these MOSFETs are determined and compared. We have investigated the temperature-dependence of the threshold voltage V_T and determined the effective mobility μ_(eff) and the field effect mobility μ_(FE). Based on Hall effect measurements, we determined independently the free electron areal density n_s, the Hall mobility μ_H and the differential Hall mobility μ_(H,diff) The density of interface states D_(it) is obtained from the Hall effect, the temperature-dependent V_T and the conductance method. The stability of both types of MOSFETs is tested under stress (V_G = ±25 V) at T = 295 K and T= 375 K.