Comparative study of boron doped gate oxide impact on 4H and 6H-SiC n-MOSFETs

In previous works, an alternative gate oxide configuration, based on a boron treatment, was proposed in order to enhance the SiO2/SiC interface quality, enabling high channel mobility n-channel 4H-SiC lateral MOSFETs. In this paper we study the effect of this treatment on 6H-SiC MOSFETs and we compare it to their 4H-SiC counterparts. The gate oxide boron treatment highly increases mobility values in 4H-SiC whereas the increase is lower in 6H-SiC. The mobility increase by the boron treatment in 4H-SiC MOSFETs is related to the decrease of near interface oxide traps (NIOTs). Then, a different NIOTs density and energy location can be seen as a possible explanation for the different mobility improvement behavior seen in both polytypes.