Effects of deposition temperature and ammonia flow on metal-organic chemical vapor deposition of hexagonal boron nitride

Abstract The use of metal-organic chemical vapor deposition at high temperature is investigated as a means to produce epitaxial hexagonal boron nitride (hBN) at the wafer scale. Several categories of hBN films were found to exist based upon precursor flows and deposition temperature. Low, intermediate, and high NH 3 flow regimes were found to lead to fundamentally different deposition behaviors. The low NH 3 flow regimes yielded discolored films of boron sub-nitride. The intermediate NH 3 flow regime yielded stoichiometric films that could be deposited as thick films. The high NH 3 flow regime yielded self-limited deposition with thicknesses limited to a few mono-layers. A Langmuir-Hinshelwood mechanism is proposed to explain the onset of self-limited behavior for the high NH 3 flow regime. Photoluminescence characterization determined that the intermediate and high NH 3 flow regimes could be further divided into low and high temperature behaviors with a boundary at 1500 °C. Films deposited with both high NH 3 flow and high temperature exhibited room temperature free exciton emission at 210 nm and 215.9 nm.