Influence of fixed charges and trapped electrons on free electron mobility at 4H-SiC(0001)/SiO₂ interfaces with gate oxides annealed in NO or POCl₃

Free electron mobility ( μ free ) in 4H-SiC(0001) MOSFETs with gate oxides annealed in NO or POCl 3 was calculated in a wide range of effective normal field ( E eff ) from 0.02 to 2 MV cm −1 , taking account of scattering by fixed charges and trapped electrons. The present calculation indicates that the Hall mobility in the high- E eff region experimentally obtained for NO-annealed MOSFETs (14 cm 2 V −1 s −1 at 1.1 MV cm −1 ) is much lower than that for POCl 3 -annealed MOSFETs (41 cm 2 V −1 s −1 ) due to severe Coulomb scattering by electrons trapped at a very high density of interface states.