Simulation and interpretation of zinc and nitrogen dopants induced defect emissions in monoclinic gallium oxide

Zinc (Zn) and nitrogen (N) are potential acceptor dopants for inducing visible emissions and p-type conductivity in monoclinic gallium oxide (β-Ga₂O₃), however, the poor understanding of these dopants and their recombination process severely limited the optoelectronic applications. Here, we investigate the zinc (Zn) and nitrogen (N) dopants-induced intraband states and the broadening of defect emission bands due to vibronic coupling of highly transparent β-Ga₂O₃ films through chemical and optical analyses, as well as density function theory. Incorporating Zn and N in β-Ga₂O₃ shifts the valence band edge towards the Fermi level and introduces band tail states above the valence band maximum. The emission band from pure β-Ga₂O₃ becomes significantly broad with the incorporation of Zn and N resulting in two additional emission bands: green luminescence (GL) and red luminescence (RL) along with the characteristic ultraviolet luminescence (UVL) and blue luminescence (BL) of pristine β-Ga₂O₃. Furthermore, the defect states responsible for these UVL, BL, GL, and RL emissions and their phonon coupling strengths are estimated by simulating the spectral line shape of these emission bands using the configuration coordinate model. The simulation results indicate that the Zn and N dopants-induced intraband states are responsible for the GL, and RL bands. These intraband states are acceptors, which provide p-type conductivity in β-Ga₂O₃ film.