Alloys Towards Opto-electronic Applications: A First Principles Study*

Metal oxide semiconductors have been intensively investigated for many applications, such as high-power electronics and solar-blind photodetectors. Despite this intense research, achieving p-type doping in Ga₂O₃ is still challenging, and presents a practical obstacle to the fabrication of p-n based devices. Alloying, e.g., with Al or In, is a promising strategy for engineering Ga₂O₃ structural and optoelectronic properties. Furthermore, incorporating Bi or Ni through alloying can yield an alternative route to p-type doping.

In this study, we investigate InGaO alloys by means of first principles using special quasi-random structures to model the substitutional disorder. The effective band structure of InGaO alloys reveals a systematic reduction of the band gap and electron effective mass as the In content is increased. In view of applications, the mechanical properties of InGaO alloys grown over β-Ga₂O₃ surfaces have been also investigated. Results are interpreted based on the site occupation preference of In atoms. Finally, we discuss the recent proposal of alloying Ga₂O₃ to engineer the band gap, pushing up the valence-band maximum and facilitating the acquisition of shallow acceptor states to achieve p-type doping.