Theoretical and experimental investigation of the atomic and electronic structures at the 4H-SiC(0001)/SiO2 interface

Abstract

Density functional theory calculations are carried out to investigate the atomic and electronic structures of the 4H -SiC(0001)/SiO 2 interface. We find two characteristic interface atomic structures in scanning transmission electron microscopy images: One is an interface in which the density of atoms at the first interfacial SiC bilayer is greater than that in the SiC substrate, while the other is an interface where the density of atoms at the first interfacial SiC bilayer is lower. Density functional theory calculations reveal that the difference in the scanning transmission electron microscopy images is a reflection of the atomic structures of these two interfaces. In addition, it has been reported that the floating states, which appear at the conduction band edge of a 4H -SiC(0001)/SiO 2 interface, affect the electronic structure of the interface and cause marked scattering of the electrons flowing along the interface [S. Iwase, C. J. Kirkham, and T. Ono, Phys. Rev. B 95, 041302(R) (2017)]. Interestingly, we find that the floating states do not appear at the conduction band edge of one of the two interfaces. These results provide physical insights into understanding and controlling the electronic structure and carrier mobility of electronic devices using wide-band-gap semiconductors.

Stabilization and self-passivation of symmetrical grain boundaries by mirror symmetry breaking

“…We focused on how to computationally investigate grain boundaries in zinc-blende CdTe, which is probably one of the simplest problems considering the number of chemical elements and symmetry of the host. We, however, believe that our strategy can be easily extended to not only grain boundaries in other polycrystalline materials [52] but also other structures likes dislocations [44,45], interfaces [53], and surfaces [54,55] by properly restricting the area of interest (e.g. a cylindrical area for dislocations).…”

Theoretical investigation of vacancy related defects at 4H-SiC(000$\bar{1}$)/SiO$_2$ interface after wet oxidation

“…1. Although considerable theoretical and experimental effort has been devoted to revealing the interface atomic structure of SiC(0001)/SiO 2 interface, [23][24][25][26][27][28][29][30] little is known about the atomic structure of of SiC(000 1)/SiO 2 interface. Since there are no experimental studies reporting that the O atoms in SiO 2 are always bonded to the C atoms of the C face, we also consider interface models where CO bonds are absent.…”

First-principles study on structure and anisotropy of high N-atom density layer in 4H-SiC

“…5]. Our earlier study noted that such impurities on the interface may reduce the carrier mobility of the MOSFET devices due to the scattering of the conduction electrons 14 . For example, in the case of nitrogen annealing on the Si face, the nitridation is expected to grow on the a-face.…”

“…In a previous work, we performed theoretical calculations using density functional theory, and investigated the atomic structure of the 4H-SiC/SiO 2 MOS interface 14 and the effects of the defects due to the thermal oxidization 15,16 . In this work, to understand the anisotropy of the nitrogen annealing, we study the stability and electronic states of the SiC, including the various configurations of the silicon vacancies (V Si ) and nitrogen defects (N C ).…”