IEEE Study Improves Design of Avalanche Photodiodes for Photodetection in the Ultraviolet Wavelength

Researchers have developed a numerical model for optimizing the design of avalanche photodiodes to detect photons in ultraviolet wavelengths

NEW YORK, Nov. 5, 2025 /PRNewswire/ — Geiger-mode avalanche photodiodes (GM-APDs) based on 4H-SiC have high single-photon detection efficiency in the deep-ultraviolet (DUV) wavelength. To reliably detect photons in higher wavelengths such as near-ultraviolet (NUV), GM-APDs need to have higher unity-gain quantum efficiency (QE). To accomplish this, researchers often employ APDs with much thicker absorber layers because these lower-energy photons are not as readily absorbed. However, this can often lead to design challenges.

In a study that was recently published in the IEEE Journal of Quantum Electronics, Dr. Jonathan Schuster from DEVCOM Army Research Laboratory, United States, and his team have developed a numerical model with a calibrated 4H-SiC material library for the development of APDs.

“APDs with much thicker absorber layers (10s of microns) must be utilized to improve the NUV response, which necessitates switching from a conventional PIN architecture (usually < 3μm thick) to a separate-absorptioncharge-multiplication (SACM) architecture. However, this involves unique challenges such as deviating from existing front-side absorber SACM architectures to a very thick backside one,” explains Dr. Schuster.

Using the numerical model, researchers designed SACM structures that are expected to have high single-photon detection efficiency in the NUV range. The researchers considered two architectural designs – non-reach-through (NRT) and reach-through (RT), with each having distinct design considerations.

“Leveraging design rules learned and reported in this paper, we have designed both types of SACM architectures: NRT-SACM APDs and RT-SACM APDs, with unity gain QE at 340 nm up to 32% and 71% respectively, while maintaining a large electric field in the multiplication layer required for Geiger-mode operation,” says Dr. Schuster.

4H-SiC avalanche photodiodes have a wide variety of applications in ultraviolet photon detection, such as solar-blind ultraviolet detection, combustion monitoring, and environmental ultraviolet monitoring. In the future, the numerical model developed here can be instrumental in designing more sensitive and efficient APDs, significantly advancing their applications.

Reference

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SOURCE IEEE Photonics Society