GeSn 320 \times 256 Focal Plane Array for Silicon-Based Short-wave Infrared Imaging

TL;DR

This paper presents a silicon-based GeSn focal plane array for SWIR imaging, achieving high detectivity and successful imaging, offering a cost-effective alternative to traditional compound semiconductor arrays.

Contribution

The work introduces a CMOS-compatible GeSn FPA with tailored bandgap, high detectivity, and first-time SWIR imaging capability on silicon, advancing cost-effective SWIR imaging technology.

Findings

Achieved a response cutoff wavelength of 2308 nm at 298 K.

Surpassed previous GeSn device detectivity, reaching 9.7×10^{11} cm·Hz^{1/2}·W^{-1} at 77 K.

Successfully captured SWIR images using the GeSn FPA with read-out circuits.

Abstract

Short-wave infrared (SWIR) imaging arrays have demonstrated great potential in applications spanning from military to civilian consumer electronics. However, the current focal plane arrays (FPAs), which are based on compound semiconductors, have limited applications in civilian circumstances due to elevated manufacturing costs and prolonged fabrication cycle time. To address this, a high-performance 320 $\times$ 256 focal plane array based on group-IV semiconductors has been designed and manufactured on a Si substrate using a complementary metal-oxide semiconductor (CMOS) compatible fabrication process. The optical absorption layer is composed of GeSn alloy, whose bandgap could be tailored by choosing the appropriate Sn concentration. In this work, a 10% Sn concentration was employed, yielding a response cutoff wavelength of 2308 nm for the Si-based photodetector, which was measured at 298 K. Moreover, a specific detectivity of 9.7 $\times$ 10$^{11}$ cm$\cdot$ Hz$^{1/2}$ $\cdot$ W$^{-1}$ has been achieved at 77 K, surpassing all previously reported GeSn devices, and rivals commercial extended InGaAs photodetectors. With the help of read-out circuits (ROIC), SWIR images have been successfully captured for the first time by using Si-based GeSn FPA. This work demonstrates the potential of group IV imaging arrays for various applications in the commercial SWIR imaging field.