Designing a porous-crystalline structure of β-Ga2O3: a potential approach to tune its opto-electronic properties

Abstract

β-Ga₂O₃ has drawn recent attention as a state-of-the-art electronic material due to its stability, optical transparency and appealing performance in power devices. However, it has also found a wider range of opto-electronic applications including photocatalysis, especially in its porous form. For such applications, a lower band gap must be obtained and an electron–hole spatial separation would be beneficial. Like many other metal oxides (e.g. Al₂O₃), Ga₂O₃ can also form various types of porous structure. In the present study, we investigate how its optical and electronic properties can be changed in a particular porous structure with stoichiometrically balanced and extended vacancy channels. We apply a set of first principles computational methods to investigate the formation and the structural, dynamic, and opto-electronic properties. We find that such an extended vacancy channel is mechanically stable and has relatively low formation energy. We also find that this results in a spatial separation of the electron and hole, forming a long-lived charge transfer state that has desirable characteristics for a photocatalyst. In addition, the electronic band gap reduces to the vis-region unlike the transparency in the pure β-Ga₂O₃ crystal. Thus, our systematic study is promising for the application of such a porous structure of β-Ga₂O₃ as a versatile electronic material.