Materials Science Forum Vol. 1190

Abstract: Synchrotron X-ray topography (XRT) combined with ray-tracing simulation was employed to examine the distribution and formation mechanisms of LAGBs in off-axis 4H-SiC wafers grown by PVT. Extensive TED-LAGB networks were observed adjacent to the facet, along with three TED-LAGBs emanating from micropipes on the left edge of the wafer. Ray-tracing simulations enabled the identification of TED Burgers vectors by correlating simulated and observed contrast configurations. The results suggest that large TED-LAGB networks near facets originate from misorientations between growth fronts of horseshoe-shaped steps incorporating prismatic slip dislocations, induced by radial temperature gradients. Similarly, LAGBs associated with micropipes arise from localized step-flow perturbations. These findings provide a revised mechanism for TED-LAGBs formation, establishing a link between their spatial distribution and growth dynamics, and offering new insights into their role in determining the quality of 4H-SiC substrates.

Abstract: Based on the analysis of the defect formation in silicon carbide polytypes in different semiconductor manufacturing processing steps, device operation and environmental-device interaction it is concluded that external material and energy fluxes are generally able to destabilize the polytype structure. The governing reason is the formation of stacking faults and instabilities of the partial dislocation associated with them. A new ansatz is proposed to describe the structural instabilities using none-equilibrium thermodynamics and the entropy production. A criterial form for polyype transitions is proposed. The developed criterial form is applied to describe observed structural instabilities occur­ring under different external actions.

Abstract: This work explores the role of implantation depth in suppressing bipolar degradation of 4H-SiC PiN diodes through proton implantation. Targeting depths aligned with active basal plane dislocations (BPDs) effectively reduces stacking-fault expansion, as confirmed by electroluminescence imaging [1,2]. From these observations, we quantified the effective range of suppression in both depth and safe operating current density. Room-temperature proton implantation (170keV, 1×10¹⁶ cm^-2) into the buffer reduced forward-voltage drift ΔV_F by 97% at 600A/cm². The implanted diode extended the safe operating current range to 1300A/cm², ~200A/cm² higher than the reference, confirming effective suppression of bipolar degradation. Once the suppression barrier, defined as a critical excess hole density threshold, was exceeded, the proton-implanted diode exhibited explosive basal plane dislocation activity, leading to the formation of multiple bar-shaped stacking faults. These active BPDs are located deeper than the proton-implant tail, at a depth of around 11.4µm; however, the threshold hole density required for their activation remains approximately the same (~ 4×10¹⁶ cm^-3) [3].