Controlled MOVPE growth of sp2-bonded BAlN alloys: Influence of precursor injection schemes on crystal structure and optical properties

Data related to the figures presented in the manuscript: Controlled MOVPE growth of sp2-bonded BAlN alloys: Influence of precursor injection schemes on crystal structure and optical properties.Summary of the research:Hexagonal boron nitride (hBN) is a promising wide-bandgap layered semiconductor for deep ultraviolet (DUV) optoelectronics, yet the lack of efficient bandgap engineering strategies has hindered its implementation in quantum well structures. In this work, we demonstrate the controlled growth of sp2-bonded boron aluminum nitride (hB1-xAlxN) alloys on sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). Two distinct growth protocols: continuous flow growth (CFG) and flow modulation epitaxy (FME) were systematically compared to reveal their impact on crystal structure, morphology, aluminum incorporation, and optical response. CFG invariably led to the formation of misoriented, porous flakes, whereas FME enabled continuous layered growth with preserved crystallinity. By varying the precursor pulsing sequence in FME, we achieved an Al incorporation up to x=0.66% and observed pronounced differences in strain distribution, defect density, and absorption characteristics. The results revealed that simultaneous pulsing of TEB and TMAl, rather than their separation, enables more efficient aluminum incorporation while preserving the sp²-bonded layered structure, as confirmed by Fourier-transform infrared spectroscopy. Absorption measurements further showed that even low Al contents modify excitonic transitions near the band edge and influence the polytype of the material. Altogether, these results highlight a new pathway for compositional tuning in layered nitrides through precise control of co-injected precursors, demonstrating the crucial role of injection protocols in governing both structural integrity and optical performance of hB1-xAlxN in the DUV spectral range.