Band alignments and polarization properties of BN polymorphs

Boron nitride can occur in the zincblende, wurtzite, and layered hexagonal phases. We use first-principles techniques based on hybrid density functional theory to study the electronic structure and polarization properties of these polymorphs. We find from the band structures that they have indirect band gaps. We report the band offsets between the polymorphs and with respect to GaN and AlN; a very small conduction-band offset between wurtzite BN and AlN is found. The piezoelectric polarization coefficients of wurtzite BN are opposite in sign to those in the other nitrides, and the magnitude of the spontaneous polarization is significantly larger.