Plasma-enhanced atomic layer deposition of N-doped GaO thin film for bandgap modulation

•N-doped GaO thin film on Si substrate was prepared at 200 °C.•The bandgap of GaO was reduced with 0.49 eV after the incorporation of N.•The energy band diagram of the GaO:N thin film was determined. Bandgap modulation is extremely important for optoelectronic and electronic devices. However, compare with Ⅱ-Ⅵ and Ⅲ-Ⅴ compound semiconductors, the ultrawide bandgap semiconductor Ga2O3 (Ⅲ-Ⅵ) faces a tough obstacle of bandgap modulation. Herein, we have prepared a N-doped GaO thin film on Si substrate through a plasma-enhanced atomic layer deposition (PEALD) method. The as-deposited GaO:N layer exhibits amorphous nature with thickness of ∼8.4 nm. The bandgap of the as-deposited GaO:N layer is adjusted to 4.31 eV, which is ∼0.49 eV smaller than the bandgap of pure Ga2O3. In addition, the photoluminescence (PL) spectra from five randomly selected points of the film layer indicate the uniformly distribution of N concentration. Subsequently, the energy band diagram of the as-deposited GaO:N layer is determined by the X-ray photoelectron spectroscopy (XPS), in which the Fermi energy level locates ∼0.81 eV below the conduction band minimum (CBM) and ∼3.5 eV above the valence band maximum (VBM). Our study raises a promising strategy for modulating the bandgap of Ga2O3, which provides potential applications in spectrum adjustable photodetector and high electron mobility transistor.