4H-SiC p-Channel MOSFETs with Epi-Channel Structure

Abstract

From a viewpoint of device application using p-channel SiC MOSFETs, control of their channel properties is of great importance. We aimed to control the electrical properties of 4H-SiC p-channel MOSFETs through locating the p-type epitaxial layer at the channel area, so called “epi-channel MOSFET” structure. We varied the dopant concentrations and the thickness of the epi-channel layer, and investigated their electrical properties. In case of heavily doped epi-channel samples, the devices indicated “normally-on” characteristics, and their channel mobility decreased slightly in comparison with the inversion-type devices. As for lightly doped epi-channel samples, the subthreshold current increased with thickness of the epi-channel layer keeping their “normally-off” characteristics. Their channel mobility also increased with thickness of the epi-channel layer. The peak value of field effect channel mobility of the sample with 2.5 μm thickness and 5×1015 /cm3 dopant concentration epi-channel was 18.1 cm2/Vs.