Growth of Zn-N Co-Doped GaO Films by a New Scheme with Enhanced Optical Properties.

Gallium oxide (GaO), as a wide-bandgap semiconductor material, is highly expected to find extensive applications in optoelectronic devices, high-power electronics, gas sensors, etc. However, the photoelectric properties of GaO still need to be improved before its devices become commercially viable. As is well known, doping is an effective method to modulate the various properties of semiconductor materials. In this study, Zn-N co-doped GaO films with various doping concentrations were grown in situ on sapphire substrates by atomic layer deposition (ALD) at 250 °C, followed by post-annealing at 900 °C. The post-annealed undoped GaO film showed a highly preferential orientation, whereas with the increase in Zn doping concentration, the preferential orientation of GaO films was deteriorated, turning it into an amorphous state. The surface roughness of the GaO thin films is largely affected by doping. As a result of post-annealing, the bandgaps of the GaO films can be modulated from 4.69 eV to 5.41 eV by controlling the Zn-N co-doping concentrations. When deposited under optimum conditions, high-quality Zn-N co-doped GaO films showed higher transmittance, a larger bandgap, and fewer defects compared with undoped ones.