High performing ITO/Ge heterojunction photodetector for broad wavelength detection

Abstract

High-performing photodetector was fabricated by the ITO/Ge heterojunction device. Due to a small bandgap Ge semiconductor, ITO/Ge photodetector showed a significantly high photoresponse for long wavelengths. For ITO/Ge photodetector fabrication, an optically transparent and electrically conductive ITO layer was deposited on a Ge substrate and spontaneously formed a rectifying junction. The HRTEM image revealed the presence of GeOx at the interface of the ITO and Ge. The XPS and UPS studies were carried out to realize the band-offset structure of ITO/Ge photodiode. When the p-type Ge and ITO are brought into contact, the Fermi levels of both the materials are lined up. Besides, the energy bands of Ge are pinned to the Fermi level of the ITO layer at the junction. The band bending effect is depicted from the band offset of the ITO/Ge photodetector. We discuss an effective method of the ITO/Ge heterojunction device fabrication and suggest a strong route for high-performing broad range wavelength (600–900 nm) photodetectors.