Probing Boron Vacancy Complexes in h-BN Semi-Bulk Crystals Synthesized by Hydride Vapor Phase Epitaxy

Hexagonal BN (h-BN) has emerged as an important ultrawide bandgap (UWBG) semiconductor (E-g similar to 6 eV). The crystal growth technologies for producing semi-bulk crystals/epilayers in large wafer sizes and understanding of defect properties lag decades behind conventional III-nitride wide bandgap (WBG) semiconductors. Here we report probing of boron vacancy (V-B)-related defects in freestanding h-BN semi-bulk wafers synthesized by hydride vapor phase epitaxy (HVPE). A photocurrent excitation spectroscopy (PES) was designed to monitor the transport of photoexcited holes from deep-level acceptors. A dominant transition line at 1.66 eV with a side band near 1.62 eV has been directly observed, which matches well with the calculated energy levels of 1.65 for the V-B-H deep acceptor in h-BN. The identification of V-B complexes via PES measurement was further corroborated by the temperature-dependent dark resistivity and secondary ion mass spectrometry measurements. The results presented here suggested that it is necessary to focus on the optimization of V/III ratio during HVPE growth to minimize the generation of V-B-related defects and to improve the overall material quality of h-BN semi-bulk crystals. The work also provided a better understanding of how V-B complexes behave and affect the electronic and optical properties of h-BN.

Automated summary

This study investigates the boron vacancy (V-B)-related defects in hexagonal BN (h-BN) using photocurrent excitation spectroscopy (PES) and temperature-dependent dark resistivity measurements. The results directly observe the energy levels of the V-B defects and further confirm their existence using other measurement techniques. The study suggests that optimizing the V/III ratio during HVPE growth can minimize the generation of V-B-related defects and improve the material quality.