Type-II superlattice LWIR detector has high detectivity and responsivity

March 24, 2021
A band-structure-engineered longwave-infrared (LWIR) heterojunction phototransistor based on a type-II superlattice has potential for astronomy, remote sensing, and other uses.

Leading-edge longwave-infrared (LWIR) photodetectors are typically based on mercury cadmium telluride (HgCdTe, or MCT), leading to high sensitivity and detection speeds, especially in the form of avalanche photodiodes (APDs). But MCT is a tough material to grow consistently; in addition, MCT APDs have low gain, necessitating high bias voltages and leading to excess spectral noise. Two-dimensional materials such as graphene, black phosphorous, and black arsenic phosphorous show some promise, but also have various disadvantages. Manijeh Razeghi and her group at Northwestern University (Evanston, IL) are taking another approach to LWIR device design that has produced the first gain-based LWIR photodetector using band-structure engineering based on a type-II superlattice material.

This new design, which, cooled to 77 K, demonstrated LWIR photodetection of 1284 A/W and a specific detectivity of 2.34 × 1013 cm Hz1/2/W at a peak detection wavelength of 6.8 μm during testing and a 1/e cutoff wavelength of 8 μm, could lead to new levels of sensitivity for next-generation LWIR photodetectors and focal-plane-array (FPA) imagers. The work could have applications in earth science and astronomy, remote sensing, night vision, optical communication, and thermal and medical imaging.

The type-II superlattice is a quantum-mechanics-based material system known for its outstanding growth uniformity and exceptional band-structure engineering (the ability to control the materials bandgap). Razeghi’s team used the new material in a heterojunction phototransistor device structure, a detection system known for its high stability, but one previously limited to shortwave and near-infrared detection. During testing, the type-II superlattice allowed each part of the photodetector to be carefully tuned to use the phototransistor to achieve high optical gain, low noise, and high detectivity. Reference: A. Dehzani et al., Light Sci. Appl. (2021); https://doi.org/10.1038/s41377-020-00453-x.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Brain Computer Interface (BCI) electrode manufacturing

Jan. 31, 2025
Learn how an industry-leading Brain Computer Interface Electrode (BCI) manufacturer used precision laser micromachining to produce high-density neural microelectrode arrays.

Electro-Optic Sensor and System Performance Verification with Motion Systems

Jan. 31, 2025
To learn how to use motion control equipment for electro-optic sensor testing, click here to read our whitepaper!

How nanopositioning helped achieve fusion ignition

Jan. 31, 2025
In December 2022, the Lawrence Livermore National Laboratory's National Ignition Facility (NIF) achieved fusion ignition. Learn how Aerotech nanopositioning contributed to this...

Nanometer Scale Industrial Automation for Optical Device Manufacturing

Jan. 31, 2025
In optical device manufacturing, choosing automation technologies at the R&D level that are also suitable for production environments is critical to bringing new devices to market...

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!