(Invited) Stacking Faults in 3C-SiC: From the Crystal Structure, to the Electrical Behavior

Abstract

Many attractive mechanical and electrical properties make silicon carbide (SiC) a material of interest in both electronic devices and sensors for nowadays technology (sustainable energies, hybrid vehicles, low power loss inverters). Silicon carbide exists in nature in several crystalline structures, called polytypes, differentiated by the stacking sequence of the tetrahedrially bonded Si-C bilayers. The only possible cubic structure, 3C-SiC, is obtained when the bilayer stacking is of the kind ABCABC..., resulting in a pure zinc-blende structure. 3C-SiC growth on Si is allowed within chemical vapour deposition (CVD) reactors, which would ensure a very high purity of the resulting product. The interface between 3C-SiC and Si is the origin of a high density of planar and volume defects, such as microtwins, anti-phase boundaries and stacking faults in the epilayer and voids in Si underneath the hetero-interface. Most of these defects, considered killers for devices, however, reduce their density, and some are totally annihilated, when very thick (several tens of microns) 3C-SiC epitaxial films are realized. The main defects that remain also after the growth of several tens of microns are the Stacking Faults (SFs). Three main SFs have been observed in 3C-SiC: the intrinsic one where only one plane is shifted with respect to the lattice position and two extrinsic SFs where two or three layers are shifted. In these last cases we observe locally the same crystallographic structure of the hexagonal polytypes: 4H-SiC and 6H-SiC. In the last period a large investigation has been done on these defects to see the crystallographic structure of these defects, the interactions between different SFs, the influence of the SFs on the internal stress of the material, the effects of several growth parameters (temperature, doping, growth rate, ...) on the density and evolution of these defects. Finally also several local electrical measurements by C-AFM has been done to understand the effect of these defects on the electrical behaviour of the devices.In Fig. 1 a three different HRTEM images of three different SFs are reported. It is possible to observe the different crystallographic structure of these defects. In Fig. 2 the interaction between these defects is reported. It is possible to observe that the SFs can annihilate or generate or close. The growth parameters have a large influence on the evolution of these defects. In Fig. 3 can be observed that, decreasing the growth rate and the growth temperature, the SFs density decreases. In Fig. 4 it is reported the effect of the doping on the SFs. Increasing the nitrogen concentration the SFs density decreases and the average length increases.At the conference more details on the SFs structure, the effect of these defects on the stress and on the electrical characteristics of the devices will be given. Figure 1