Chemical Vapor Deposition of Boron-Incorporated Graphitic Carbon Nitride Film for Carbon-Based Wide Bandgap Semiconductor Materials

This article discusses the growth of B atoms incorporated into the graphitic carbon nitride (g-C3N4) thin films on c-plane sapphire substrates at various growth temperatures by thermal chemical vapor deposition (CVD) using melamine and ammonia borane as precursors. The B incorporation is achieved at a growth temperature of 618 degrees C, which is slightly higher than the optimal growth temperature of g-C3N4 thin films. The signal peak for the B 1s core level attributed to B-N bonds is observed by X-ray photoelectron spectroscopy, indicating the realization of B incorporation into g-C3N4 films. With an increase in the growth temperature up to 650 degrees C, a monotonically increasing B composition and a decreasing C composition are observed, implying that B atoms are incorporated into g-C3N4 by the substitution into C sites. A shift of photoluminescene (PL) peak energy is observed. The PL peak shifts from 2.75 eV for unintentionally doped thin film to 3.60 eV for B-incorporated thin films with a composition of 8.0%. The B composition dependence of PL peak energies is in good agreement with the quadratic function, suggesting that the bandgap bowing occurs due to B incorporation into the g-C3N4 thin films as in conventional compound semiconductor alloys.