Structural and photoluminescence properties of Co-Sputtered p-type Zn-doped β-Ga2O3 thin films on sapphire substrates

Abstract

This work discusses the growth characteristics, composition, and photoluminescence properties of Zn-doped Ga2O3 (ZnGaO) films. The idea of doping of Zn divalent cation in β-Ga2O3 is to modulate the n-type conductivity of β-Ga2O3 to p-type. Therefore, a series of ZnGaO films with varying Zn contents have been deposited on sapphire substrates using co-sputtering of Ga2O3 and Zn targets at the substrate temperature of 400 °C. The X-ray diffraction analysis revealed that divalent Zn dopant is stable up to 8.62% in ZnGaO films. The X-ray photoelectron spectroscopy defined the increasing amount of Zn content in ZnGaO films. The lowest defect formation energy per atom by first-principles calculations indicates that the favourable site of Zn atoms is substitutional Ga tetrahedral site (T-site) in ZnGaO. The photoluminescence (PL) spectra exhibited that the peak emission wavelength of β-Ga2O3 can be shifted with the inclusion of divalent Zn dopant in Ga2O3 films, which is in accordance with the energy diagram and charge density distribution, indicating the Zn substituted T-site Ga are leading to more defect states, and inducing green luminescence in PL spectra. The ZnGaO films exhibited positive Hall coefficient, which verifies the p-type nature of films. ZnGaO films demonstrate a unique ability to realize p-type characteristics among emerging wide bandgap semiconductors, extending its applications at the forefront of contemporary optoelectronics technologies.