Influence of photonic crystals on the performance parameters of GeSn vertical-structure photodiodes

In recent years, use of photonic crystals has been recognized as a viable approach to resolve the contradiction between operating speed and light absorption in vertical-structure photodiodes. In this paper, we present a photonic crystal that enhances the responsivity of a GeSn pin photodiode in the near-infrared region of the spectrum. Additionally, the effects of this photonic crystal on the most important properties of the GeSn pho-todiodes are studied. Based on measurement and analysis of the device's dark current, responsivity, and speed characteristics, the photonic crystal structure reduces the dark current by approximately 57%, increases the responsivity at 1550 nm and 1650 nm by factors of 2.4 and 3.9, respectively, and increases the 3dB bandwidth at 1550 nm by a factor of approximately 2.6. These results demonstrate that photonic crystals have good appli-cation value for solution of the contradiction between the light absorption and operating speed characteristics of high-speed photodiodes.