Demonstration and analysis of channel mobility, trapped electron density and Hall effect at SiO₂/SiC (0$\bar{3}$3$\bar{8}$) interfaces

Abstract

Low interface state density (Dit) and high field-effect mobility (μfe) at SiO2/4H-SiC (0 3 ) Metal-oxide-semiconductor (MOS) interfaces are known. In order to understand the behavior and the scattering mechanisms induced electrons in more detail, we fabricated the Hall-bar lateral MOSFETs on the 4H-SiC (0 3 ) substrate with various channel doping concentrations and evaluated the trapped electron densities and the Hall mobilities by split capacitance–voltage and Hall-effect measurements. Our results demonstrated that more than 80% of the induced electrons at the SiO2/4H-SiC MOS (0 3 ) interfaces contribute to the current conduction as the free electrons. The majority of the electron traps seemed to be located mainly at the edge of the conduction band because the trapped electron density increased around the threshold voltage and was saturated in the high gate voltage region.

First-principles study on structure and anisotropy of high N-atom density layer in 4H-SiC

“…The decrease of the mobility is caused by the a dense trapped state created in the oxidation process on the SiC/SiO 2 interface 4,5 . To reduce the density of traps, a passivation treatment with nitrogen has been used and improvement in the mobilities µ = 30 ∼ 80 cm/V • s has been achieved 5,6 . This nitrogen annealing process exhibits an anisotropic behavior with respect to the crystal faces 7,8 .…”

Dipole Scattering at the Interface: The Origin of Low Mobility observed in SiC MOSFETs

“…To address this issue, many studies have been devoted to the causes of the low observed mobility in SiC MOSFETs [4][5][6][7]. It has been established that there are two causes of the low mobility in SiC MOSFETs [6,[8][9][10][11][12][13]. One cause is the reduction in the free electron density (n free s ) in the MOS channel caused by a high density of interface states (D it ) near the bottom of the conduction band (E C ) [6,[8][9][10].…”

“…The second cause is the low free electron mobility (µ free ) of the remaining mobile electrons in the MOS channel [8,9,[11][12][13][14][15][16]. It has been found that the high density of D it near E C can be reduced and thus the n free s can be improved [8][9][10]. However, the possible increase of the µ free is limited [8][9][10].…”

“…It has been found that the high density of D it near E C can be reduced and thus the n free s can be improved [8][9][10]. However, the possible increase of the µ free is limited [8][9][10]. Even in the case of SiC MOSFETs on 4H-SiC(0 33 8) faces annealed in nitric oxide, the µ free is only ~100 cm 2 /Vs [9,10], which is much smaller than the mobility expected based on the bulk mobility (~1000 cm 2 /Vs) [17][18][19].…”

“…However, the possible increase of the µ free is limited [8][9][10]. Even in the case of SiC MOSFETs on 4H-SiC(0 33 8) faces annealed in nitric oxide, the µ free is only ~100 cm 2 /Vs [9,10], which is much smaller than the mobility expected based on the bulk mobility (~1000 cm 2 /Vs) [17][18][19]. For further improvements in the performance of SiC MOSFETs, it is essential to identify the origin of the low µ free .…”