Interface properties of NO-annealed 4H-SiC (0001), (112¯), and (11¯00) MOS structures with heavily doped p-bodies

Abstract

We investigated electrical characteristics of nitric oxide (NO)-annealed silicon carbide (SiC) (0001), (112¯0), and (11¯00) metal-oxide-semiconductor field effect transistors (MOSFETs) with heavily doped p-bodies (NA = 1 × 1017–3 × 1018 cm−3). Regardless of crystal faces or off-direction, the channel mobility decreased for higher acceptor density. We evaluated the interface state density (Dit) very near the bottom edge of 2-dimensional density of states (2D-DOS) in the conduction band of SiC from the low-temperature subthreshold slope of the MOSFETs. When the acceptor density of the p-body of the MOSFET is increased, the energy levels of 2D-DOS increase due to a stronger quantum confinement effect. Accordingly, the carriers in the heavily doped channel are influenced by the interface states located at higher energy levels. In the SiC MOS structures, the Dit values significantly increase near the conduction band edge (EC). Thus, MOSFETs on heavily doped p-bodies are affected by the higher density of Dit, leading to substantially lower mobility.