III-nitride wide bandgap semiconductors have been at the center stage of the semiconductor R & D effort over the last two decades.  Photonic/electronic devices based on III-nitrides, including UV/blue/green/white light emitting diodes (LEDs), violet/blue laser diodes (LDs), UV detectors, and high power/temperature transistors, have been successfully realized and commercialized.

Among the members of the III-nitrides, BN is the least studied and understood. BN exists in three crystalline forms (hexagonal, cubic and wurtzite). The sp²-bonded hexagonal form (h-BN) is the most stable phase when synthesized at any temperature under ambient pressure. Its extraordinary physical properties, such as ultra-high chemical stability, thermal conductivity, electrical resistivity, and band gap (E_g ~ 6.5 eV) make h-BN the material of choice for many emerging applications. Due to its close lattice match to graphite, h-BN is being recognized as the most suitable substrate/dielectric/separation layer for 2D electronics and optoelectronics. As such, much efforts in the synthesis of h-BN have been largely focused on mono- or a few layers of h-BN in the past.

In this presentation, I will summarize recent progress in the growth of wafer-scale h-BN epilayers with a few um in thickness by metal-organic chemical vapor deposition (MOCVD). The basic properties of h-BN epilayers will be discussed in comparison with other nitride semiconductors, in particular AlN.  H-BN shows the unique qausi-2D nature with exceptionally high density of states (DOS) and large exciton binding energy (around 740 meV), which results in high optical absorption and emission intensity. P-type conduction in h-BN and diode behaviors in the p-n junction structures consisting of p-type h-BN and n-type Al-rich AlGaN heterostructures have been demonstrated, which could potentially address the intrinsic problem of low p-type conductivity in Al-rich AlGaN for DUV photonic devices. The potential applications of h-BN for deep UV emitters and detectors, 2D templates/dielectric/separation layers, and solid-state neutron detectors will also be discussed.