Investigation of basal plane dislocation nucleation in Al-doped p-type 4H-SiC using nanoindentation and molecular dynamics

High-quality p-type 4H-SiC crystals serve as the fundamental material for n-channel SiC insulated gate bipolar transistors, which are essential for ultra-high voltage power devices. However, the development of p-type 4H-SiC is hindered by crystal defects, particularly dislocations. Among all types of dislocations, basal plane dislocation (BPD) is the most common. This study employs nanoindentation to investigate BPD nucleation in p-type 4H-SiC, supported by molecular dynamics simulations to analyse the stress-strain behaviour and the effect of aluminium (Al) doping. Nanoindentation experiments reveal that p-type 4H-SiC exhibits easier plastic deformation with the increase of Al doping concentration. This deformation primarily involves the formation of BPD, stacking faults, and crystallographic transformations. Molecular dynamics simulations further elucidate the mechanisms behind these observations, showing that Al doping facilitates BPD nucleation, with a higher incidence rate at greater Al doping concentrations. A key finding of this study is that the primary occurrence of BPD in p-type 4H-SiC stems from the formation of Si-Al bonds, which is distinct from the formation of Si-Si bonds during BPD nucleation in nominally undoped 4H-SiC. This distinction highlights the impact of Al doping on the atomic-scale interactions and defect formation processes within the crystal lattice. This study advances the understanding of BPD behaviour in p-type 4H-SiC and provides a foundation for its industrial applications.