An Alternative to Compound Semiconductors Using a Si-Based IR Detector

Abstract

Though infrared (IR) photodetection is popular, it faces several problems. First, the main materials, compound semiconductors, require high temperature, low pressure, and high energy consumption facilities. Second, compound semiconductor elements are rare on earth. Third, compound semiconductors are difficult to integrate with Si-based integrated circuit (IC) manufacturing process. To overcome these problems, we utilized a Si-based Schottky junction and internal photoemission to break the detection limit of a Si photodetector. The spectral detection limit extends from 1100 nm, the bandgap wavelength of Si, to ca. 1600 nm, the Schottky barrier wavelength of the metal/Si junction. The Schottky junction is composed by Ag and n-type Si through simple thermal evaporation. The light incident direction, metal thickness, and device temperature were analyzed. As a result, under normal temperature and pressure, the Schottky barrier height of the Ag/Si junction is 0.742 eV. The detection limit is 1670 nm. If the 1550-nm laser is a detected light source illuminating from the metal film, the responsivity is 0.02122 mA/W. If the same detected light source illuminates from the Si substrate, the responsivity improves to 0.04567 mA/W due to the light absorption enhancement. Furthermore, if the metal thickness is increased to 100 nm, the responsivity increases to 1.242 mA/W, which is about 585.3% of the original value. In addition, the influence of the temperature on the electric properties of the devices indicates that a Ag/Si Schottky device could be a candidate for temperature detection.