Development and characterization of a ZnO/Ge photodiode for optical radiation measurements in the near infrared

Abstract

The metrology group of radiometric and pyrometric measurements of INSAT include among others the development of detectors that will be used as a standard in the MMA Laboratory for optical radiation measurements in the visible and infrared spectral range. In this work, we present the design and realization of a detector for near infrared radiation measurements: it is a photodiode ZnO/Ge based on a germanium junction and a thin layer of zinc oxide. Then we electrically and optically characterized the photodiode thus realized, for which we developed an energy band diagram. The obtained results have allowed us to note an improvement in the optical and electrical characteristics of the ZnO/Ge photodiode, compared to those performed in our laboratory and based on single Germanium. The reflectivity is reduced by about 9% for the wavelength range of 800 nm to 2000 nm. The shunt resistance increases from 95 Ω to 12.915 kΩ. However, the series resistance increases from 1.08 Ω to 36 Ω but it is still an acceptable value. The proposed energy band diagram explains the charge carrier transport phenomena for our structure and it is in good agreement with experimental results.