Comparison of the electrical channel properties between dry- and wet-oxidized 6H-SiC MOSFETs investigated by Hall effect

Laube, M.*; Pensl, G.*; Lee, K. K.; Oshima, Takeshi

The electrical properties of n-channel 6H-SiC MOSFETs have been studied by temperature-dependent current-voltage and Hall effect measurements. The MOS transistors are either wet (sample A) or dry oxidized followed by a post-annealing step at 1100C and a pyrogenic reoxidation at 800C (sample B). Higher drain transconductance and saturation currents are observed in sample B. The Hall effect investigations show that this improvement in the performance of the MOS transistors (sample B) is caused by a lower degree of trapping of free electrons. The density of interface traps D close to the conduction band edge has been determined from the shift of the threshold voltage V as a function of the temperature and from the Hall effect results. D is about two times lower in sample B. The room temperature value of the electron Hall mobility is determined to be about 60 cm/Vs for both samples; it increases with decreasing temperature.