Al-doped and in-doped ZnO thin films in heterojunctions with silicon

• Al-doped and In-doped ZnO thin films have been deposited onto Si.
• In-doped ZnO/p-Si heterojunction showed poor rectifying behaviour.
• Al-doped ZnO/p-Si heterojunction showed a good rectifying at room temperature.
• The carriers transport mechanisms was controlled by interfacial and volume defects.

The undoped, Al-doped and In-doped ZnO thin films were deposited by ultrasonic spray pyrolysis technique, onto glass and p-Si substrates and the physical properties of the films were investigated. The X-ray diffraction, optical analysis and electrical characterisations, indicate that the films were polycrystalline with hexagonal würtzite type structure and revealed that the aluminium doping deteriorates the crystalline and optical properties and enhances the electrical conductivity whereas indium doping improves all properties. The transport mechanism controlling the conduction through the heterojunctions was studied. For the heterostructures, the temperature dependent current–voltage characteristics showed rectifying behaviour in the dark, but current transport mechanism is not the same for all heterojunctions. Therefore, the presence of the interface states and volume defects are identified as limiting factors for obtaining a high quality heterojunction interface.