Interface state density of SiO2/p-type 4H-SiC (0001), (11(2)over-bar0), (1(1)over-bar00) metal-oxide-semiconductor structures characterized by low-temperature subthreshold slopes

Interface properties of heavily Al-doped 4H-SiC (0001) (Si-face), (11 (2) over bar0) (a-face), and (1 (1) over bar 00) (m-face) metal-oxide-semiconductor (MOS) structures were characterized from the low-temperature gate characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs). From low-temperature subthreshold slopes, interface state density (D-it) at very shallow energy levels (E-T) near the conduction band edge (E-c) was evaluated. We discovered that the D-it near E-c (E-c - 0.01 eV < E-T< E-c) increases in MOS structures with higher Al doping density for every crystal face (Si-, a-, and m-face). Linear correlation is observed between the channel mobility and D-it near E-c, and we concluded that the mobility drop observed in heavily doped MOSFETs is mainly caused by the increase of Dit near Ec. Published by AIP Publishing.