On Separating Oxide Charges and Interface Charges in 4H-SiC Metal-Oxide-Semiconductor Devices

Abstract

We have investigated the distribution of oxide traps and interface traps in 4H Silicon Carbide MOS devices. The density of interface traps, Dit, was characterized using standard C-V techniques on capacitors and charge pumping on MOSFETs. The number of oxide traps, NOT, was then calculated by measuring the flatband voltage VFB in p-type MOS capacitors. The amount that the measured flatband voltage shifts from ideal, minus the contributions due to the number of filled interface traps Nit, gives an estimate for the number of oxide charges present. We found Dit to be in the low 1011cm−2eV−1 range in midgap and approaching 1012 −1013cm−2eV−1 near the band edges. This corresponds to an Nit of roughly 2.5 ⋅1011cm−2 for a typical capacitor in flatband at room temperature. This data combined with measurements of VFB indicates the presence of roughly 1.3 ⋅1012cm−2 positive NOT charges in the oxide near the interface for our samples.