Ab Initio Prediction of Ultra‐Wide Band Gap BxAl1−xN Materials

Ultra‐wide bandgap (UWBG) materials are poised to play an important role in the future of power electronics. Devices made from UWBG materials are expected to operate at higher voltages, frequencies, and temperatures than current silicon and silicon‐carbide‐based devices and can even lead to significant miniaturization of such devices. In the UWBG field, aluminum nitride and boron nitride have attracted great interest; however, the BxAl1−xN alloys are much less studied. In this work, using first‐principles simulations combining density‐functional theory and the cluster expansion method, the crystal structure of BxAl1−xN alloys is predicted. Seventeen ground state structures of BxAl1−xN with formation energies between 0.11 and 0.25 eV atom‐1 are found. All of these structures are found to be dynamically stable. The BxAl1−xN structures are found to have predominantly a tetrahedral bonding environment; however, some structures exhibit sp2 bonds similar to hexagonal BN. This work expands knowledge of the structures, energies, and bonding in BxAl1−xN which aids their synthesis, the innovation of lateral or vertical devices, and discovery of compatible dielectric and Ohmic contact materials. Using first‐principles simulations, it is predicted that alloys of wurtzite‐AlN and wurtzite‐BN can exist as highly mismatched BxAl1−xN alloys at 17 B‐compositions for x = 0 to 1. It is found that the BxAl1−xN alloys largely maintain the sp3 bonding seen in wurtzite AlN and BN but with substantial distortion in the tetrahedral bonds and the presence of sp2 B–N bonding in one structure.