GeSn Waveguide Photodetectors with Vertical p–i–n Heterostructure for Integrated Photonics in the 2 μm Wavelength Band

Abstract

The 2 μm wavelength band (1800–2100 nm) emerges as a promising candidate for next‐generation optical communication. As a result, silicon photonic platforms acquire great interest since they offer the ultimate minimization of photonic systems for 2 μm band applications. However, the large bandgap and indirectness of the band structure of the conventional SiGe alloy prevent their utilization for efficient photodetection in the 2 μm wavelength band. To overcome this drawback, complementary metal‐oxide semiconductor (CMOS)‐compatible GeSn waveguide photodetectors (WGPDs) with a vertical p–i–n heterojunction configuration that can operate in the 2 μm wavelength band is demonstrated. The proposed photodetector incorporates 5.28% Sn into the GeSn active layer, which redshifts the photodetection range to 2090 nm. In addition, the longer light–matter interaction length and good optical confinement of the proposed GeSn WGPD enhance the optical responses significantly. As a result, the proposed GeSn WGPD achieves a responsivity up to 0.52 A W−1 and a detectivity up to 7.9 × 108 cm Hz½ W−1 in the 2 μm wavelength band at room temperature. These promising results indicate that the developed GeSn WGPDs are promising candidates for integrated photonics in the 2 μm wavelength band.