Hexagonal boron nitride for deep UV photonics

Hexagonal boron nitride (h-BN) possesses extraordinary physical properties including wide bandgap (Eg ∼ 6.5 eV), high temperature stability and corrosion resistance, and large optical absorption and emission, and thermal neutron capture cross section. In addition, h-BN is a material with a very low dielectric constant, but having a very high dielectric strength. Due to its similar lattice constant with graphene, h-BN is an ideal template and dielectric separation layer in graphene devices. Furthermore, having a hexagonal layered-structure, h-BN represents an ideal platform for probing fundamental 2D properties in semiconductors. In comparison to AlN, p-type h-BN appears to be easier to obtain [1–3]. Currently, the most outstanding issue for achieving high performance deep UV emitters based on III-nitrides is the low p-type conductivity of Al-rich AlGaN. This issue is caused by the large acceptor activation energies (EA) in Al-rich AlxGa1−xN (as large as 500 meV in AlN) [3–6]. The attainment of p-type h-BN could potentially overcome the intrinsic problem of low p-type conductivity in Al-rich AlGaN for deep UV photonic devices. Wafer-scale h-BN epilayers (up to 2-inch in diameter) have been successfully synthesized by MOCVD [1–3, 7–9].