High‐Detectivity GeSn Mid‐Infrared Photodetectors for Sensitive Infrared Spectroscopy

Abstract

Infrared (IR) spectroscopy is a powerful, nondestructive analytical technique that requires cost‐effective and highly sensitive IR photodetectors (PDs). Herein, complementary metal‐oxide‐semiconductor (CMOS)‐compatible GeSn p–i–n PDs with record‐high detectivity (D*) are presented, offering a broad photodetection range that spans the mid‐IR region. With 10% Sn incorporation, the photodetection range extends to 2680 nm. By introducing a composition‐graded GeSn buffer to enhance the material quality and increasing the thickness of the GeSn active layer to 1490 nm, optical responsivity and dark current are significantly improved, thereby achieving record‐high D* values of 3.15×109 cm·Hz1/2 W−1 and 1.19×1010 cm·Hz1/2 W−1 at T = 300 K and T = 77 K, respectively. Leveraging these record‐high D* levels, the capability of GeSn PDs in IR spectroscopy is demonstrated, which can resolve weak photoluminescence from Ge, confirming their effectiveness for sensitive IR detection.

Keywords

• detectivity
• GeSn alloys
• infrared spectroscopy
• mid‐infrared
• photodetectors