Influence of indium concentration on the structural and optoelectronic properties of indium selenide thin films

• The influence of indium concentration on the structural, optical and electrical properties was studied.
• The β-phase can persist at room temperature in the In-rich films.
• The β-phase has distinct optical and electrical properties from the γ-phase.
• Visible-light photodetector based on film γ-In2Se3 shows a fast, reversible, and stable response.

We have grown indium selenide thin films using magnetron sputtering method. The influence of indium concentration on the structural, optical and electrical properties was studied. The concentration of indium in indium selenide thin films was varied by adjusting the sputtering power from 40 to 80 W while keeping the substrate temperature and argon pressure constant. The β-phase, which only exists at elevated temperatures in bulk single crystals, can persist at room temperature in the In-rich films. The β-phase thin film with smaller band gap has an electrical resistivity about four orders of magnitude lower than that of the γ-In2Se3 thin film, which is also stable at room temperature. Furthermore, the single-phase γ-In2Se3 thin film was then assembled in visible-light photodetector which shows a fast, reversible, and stable response. These results indicate the possibility of using γ-In2Se3 thin film in various next-generation photoelectric and optical-memory applications.