Track synthesis, materials and catalysis as it is published.
Search papers, labs, and topics across Lattice.
This work employs hybrid density functional methods to model group-III acceptors (B and Al) in 4H-SiC, quantifying their electronic structure, formation energies, and carrier capture kinetics. The study reveals that $\textrm{B}_{\textrm{Si}}$ exhibits significant electron and hole capture cross sections, suggesting it as a primary cause of minority-carrier lifetime degradation in boron-contaminated n-type 4H-SiC. Additionally, a novel donor transition for $\textrm{B}_{\textrm{C}}$ is predicted, which could further impede device performance by reducing free-hole concentration and increasing scattering.
Boron, not aluminum, is the primary culprit for lifetime degradation in n-type 4H-SiC due to its unusually large carrier capture cross sections.
Accurate modeling of p-type dopants in 4H-SiC is essential for understanding the mechanisms governing doping efficiency and carrier transport. In this work, we revisit the electronic structure of boron- and aluminum-related acceptors using hybrid density functional methods. Besides defect formation energies and thermodynamic transition levels, we present a quantitative look into the carrier capture kinetics within the multi-phonon emission framework. Our results reveal striking differences between the two most relevant p-type dopants. While $\textrm{B}_{\textrm{Si}}$ and $\textrm{B}_{\textrm{C}}$ exhibit nearly identical formation energies, consistent with the occurrence of both defects, the formation energy of $\textrm{Al}_{\textrm{C}}$ under intrinsic conditions is approximately 6.5 eV higher than that of $\textrm{Al}_{\textrm{Si}}$, confirming previous findings that the former is unlikely to occur. We further find that $\textrm{B}_{\textrm{Si}}$ possesses large electron and hole capture cross sections, identifying it as a plausible source of minority-carrier lifetime degradation of n-type material contaminated with boron. In addition, we predict a previously unexplored donor transition for $\textrm{B}_{\textrm{C}}$. If experimentally confirmed, this defect would represent additional problems to both p-type doped and boron contaminated 4H-SiC, not only because of its ineffectiveness as an electric dopant, but also due to trapping of up to two free holes, reducing the free-hole concentration and increasing scattering effects.