Evaluation of the Impact of Al Atoms on SiO_2/SiC Interface Property by Using 4H-SiC n~+-Channel Junctionless MOSFET

摘要

To investigate the impact of Al atoms on channel mobility at SiO_(2)/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 (m_(eff)) of n~(+)-channel junctionless MOSFET without Al doping was estimated to be 14.9 cm~(2)/Vs, which is higher than inversion-mode MOSFET fabricated with the same gate oxidation condition (3.1 cm~(2)/Vs). The m_(eff) values of the MOSFETs with low Al doping concentration (5´10~(17) and 1´10~(18) cm~(-3)) were almost the same as that of Al-free MOSFET, and the device with the highest Al doping (5´10~(18) 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 SiO_(2)/SiC interface property.