The B-III-N alloys have not been studied extensively as compared to conventional III-nitride AlGaInN alloys. However, due to the large and tunable bandgap, tunable lattice constant, and many other electronic properties, this emerging material system has enormous potentials for DUV-IR optoelectronics and power electronics devices. In this presentation, some of the latest research progress of the B-III-N alloys will be discussed, covering from epitaxial growth, microscopic characterization to electronic properties.

The TMA and NH3 preflow processes have been critical for the AlN MOVPE process on sapphire, in that they pre-condition the sapphire substrates for the Al-polar epitaxy. Although the mechanism of the NH3 preflow has been thoroughly studied and clear, that of the TMA preflow has been a bit mysterious. Some MOVPE scientists have hypothesized that the TMA preflow resulted one or more than one layers of Al or Al-rich layers on sapphire surface, which further leads to the growth of Al-polar AlN. I will present our model of the TMA preflow based on systematic electron microscopy studies.