High Mobility 4H-SiC MOSFETs Using Lanthanum Silicate Interface Engineering and ALD Deposited SiO2

In this work, we have developed a novel gate stack to enhance the mobility of Si face (0001) 4H-SiC lateral MOSFETs while maintaining a high threshold voltage. The gate dielectric consists a thin lanthanum silicate layer at SiC/dielectric interface and SiO2 deposited by atomic layer deposition. MOSFETs using this interface engineering technique show a peak field effect mobility of 133.5 cm(2)/Vs while maintaining a positive threshold voltage of above 3V. The interface state density measured on MOS capacitor with lanthanum silicate interfacial layers is reduced compared to the capacitors without the silicate. It is shown that the presence of the lanthanum at the interface reduces the formation of a lower quality SiOx interfacial layer typically formed at the SiC surface during typical high temperature anneals. This better quality interfacial layer produces a sharp SiC/dielectric interface, which is confirmed by cross section Z-contrast STEM images.