Evaluation of the Impact of Al Atoms on SiO2/ SiC Interface Property by Using 4H-SiC n+-Channel Junctionless MOSFET

To investigate the impact of Al atoms on channel mobility at SiO2/SiC interface, we fabricated the junctionless metal-oxide-semiconductor field-effect transistors (MOSFETs), in which thin n+-SiC epitaxial layers with and without Al+ ion implantation were used as a channel, and compared their electrical characteristics. The effective mobility (meff) of n+-channel junctionless MOSFET without Al doping was estimated to be 14.9 cm2/Vs, which is higher than inversion-mode MOSFET fabricated with the same gate oxidation condition (3.1 cm2/Vs). The meff values of the MOSFETs with low Al doping concentration (5´1017 and 1´1018 cm-3) were almost the same as that of Al-free MOSFET, and the device with the highest Al doping (5´1018 cm-3) exhibited slight mobility degradation of about 15% compared to the other devices. Hall mobility in thick n+ layer with the highest Al doping was also slightly degraded, suggesting that Al atoms in the channel are not the major cause of degraded SiO2/SiC interface property.