Improved interface trap density close to the conduction band edge of a-Face 4H-SiC MOSFETs revealed using the charge pumping technique

We study the interface properties of 4H silicon carbide Si-face (0001) and a-face (112̅0) power MOSFETs using the charge pumping technique. MOSFETs produced on the a-face show a higher electron mobility than Si-face devices, although their charge pumping signal is 5 times higher, indicating a higher interface/border trap density. We show the main contribution to the interface/border trap density on a-face devices originates from deep states in a wide range around midgap, whereas Si-face devices show a higher and exponentially increasing interface/border state density close to the conduction band edge of 4H silicon carbide, resulting in reduced mobility.