Large wafer-level two-dimensional h-BN with unintentional carbon doping grown by metalorganic chemical vapor deposition

Large wafer-level hexagonal boron nitride (h-BN) was grown on sapphire by MOCVD in a pulse epitaxy mode. Comprehensive materials characterizations were performed on these samples including Fourier infrared spectroscopy, X-ray diffraction, Transmission Electron Microscope (TEM), and X-ray photoelectron spectroscopy. It is indicated that the BN film is hexagonal crystal phase with sp2 B–N bond and the content of B and N elements is about 1:1. The growth model of the h-BN on sapphire by MOCVD was proposed. A small amount of unintentionally doped carbon element was characterized in the h-BN film through XPS and optical absorption spectrometer analysis. The content of carbon was positively correlated with the flow rate of Triethyl-borane (TEB). The absorption band edge of h-BN doped carbon is about 219 nm and the band gap is 5.65 eV. According to first-principles calculations, C replacing the positions of N atoms in h-BN causes the absorption peak of the impurity level at 295 nm. Meanwhile, two-dimensional interlayer Van der Waals (vdW) characteristics of h-BN were observed, on account of the h-BN self-separation phenomenon that occurred on the sapphire, the upper AlN layer on the h-BN layer could be peeled from the sapphire.