Germanium–tin (Ge1–x Sn x ) photodetectors for 2 μm wavelength band

Abstract

Abstract Germanium–Tin (Ge1–x Sn x ) alloy, due to its attractive and interesting properties, is promising for many applications in photonic devices and systems. Particularly, the bandgap of Ge1–x Sn x can be tuned by engineering the Sn compositions, thereby extending the photodetection range larger than 1.55 μm and is beyond what can be achieved by Ge. Together with the advantages of easy integration and compatibility with current mainstream Si-based complementary metal-oxide-semiconductor technology as well as cost competitiveness over III–V-based materials, Ge1–x Sn x photodetectors enable Si photonics operating at 2 μm wavelength range for optical communication, image sensors for night vision and medical diagnostic, etc. In this article, we review the recent progress of Ge1−x Sn x -based photodetectors with the main focus at the wavelength of ∼2 μm, including high-speed p-i-n photodetectors and various high responsivity photodetectors having an internal gain. We also discuss the challenges and opportunities for Ge1–x Sn x photodetectors from both materials and devices perspectives.