Suppression of stacking fault expansion in a 4H-SiC epitaxial layer by proton irradiation

Abstract

SiC bipolar degradation, which is caused by stacking fault expansion from basal plane dislocations in a SiC epitaxial layer or near the interface between the epitaxial layer and the substrate, is one of the critical problems inhibiting widespread usage of high-voltage SiC bipolar devices. In the present study, we investigated the stacking fault expansion behavior under UV illumination in a 4H-SiC epitaxial layer subjected to proton irradiation. X-ray topography observations revealed that proton irradiation suppressed stacking fault expansion. Excess carrier lifetime measurements showed that stacking fault expansion was suppressed in 4H-SiC epitaxial layers with proton irradiation at a fluence of 1 × 1011 cm−2 without evident reduction of the excess carrier lifetime. Furthermore, stacking fault expansion was also suppressed even after high-temperature annealing to recover the excess carrier lifetime. These results implied that passivation of dislocation cores by protons hinders recombination-enhanced dislocation glide motion under UV illumination.

Suppression of stacking-fault expansion in 4H-SiC PiN diodes using proton implantation to solve bipolar degradation

“…The reduction in carrier lifetime also influences the suppression of expansion, and proton implantation reduces carrier lifetime 32 , 36 . We observed carrier lifetimes in a 60 µm-thick epitaxial layer with 10 14 cm −2 proton implantation.…”

“…In contrast, in the case of the lightest element, hydrogen, an ion (proton) can be implanted at a depth of more than 10 µm in 4H-SiC using a MeV-class accelerator. Therefore, if proton implantation affects the pinning of PDs, then it can be used to suppress the expansion of BPDs in the substrates 36 . However, proton implantation can damage 4H-SiC and result in the deterioration of device performance 37 – 40 .…”

Suppression of partial dislocation glide motion during contraction of stacking faults in SiC epitaxial layers by hydrogen ion implantation

“…35,36) Recently, we have reported that proton irradiation, which is commonly used in semiconductor processing, can suppress SF expansion in the SiC epitaxial layer driven by ultraviolet (UV) illumination and forward bias application. 21,37) Although we carefully separated the effect of change in carrier lifetimes on the driving force of SF expansion and the effect of the pinning of dislocations by proton implantation, the relationship between dislocation mobility and proton implantation has remained unclear. In the present study, we investigated the contraction behavior of SFs subjected to proton implantation and revealed the relationship between dislocation mobility and proton implantation.…”

“…The detailed hydrogen density profile is shown in Ref. 37. After the proton implantation, the specimens were heated to 873 K in a nitrogen atmosphere for 10 min.…”

“…Note that the driving force for the contraction of SFs during annealing is never influenced by proton implantation, as is the case for the expansion of SFs by UV illumination. 37) Reduction of carrier lifetime has also no influence on the contraction behavior of SFs. Therefore, the current results clearly indicate that proton implantation evidently suppressed the glide motion of partial dislocations.…”