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) metal-oxide-semiconductor field-effect transistors (MOSFETs) with gate oxides annealed in NO or POCl3 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 cm2 V−1 s−1 at 1.1 MV cm−1) is much lower than that for POCl3-annealed MOSFETs (41 cm2 V−1 s−1) due to severe Coulomb scattering by electrons trapped at a very high density of interface states.