Avalanche Photodetectors with Photon Trapping Structures for Biomedical Imaging Applications

TL;DR

This paper demonstrates that integrating photon trapping nanostructures into avalanche photodiodes significantly improves their photon absorption, gain, and timing performance across the visible spectrum, advancing biomedical imaging capabilities.

Contribution

The study introduces photon trapping nanostructures into silicon avalanche photodiodes, achieving substantial enhancements in detection efficiency and timing for biomedical imaging applications.

Findings

30-fold gain increase at 850 nm wavelength

Detection efficiency increased from 54% to 82% at 450 nm

Reduced pulse response time by 50% near breakdown voltage

Abstract

Enhancing photon detection efficiency and time resolution in photodetectors in the entire visible range is critical to improve the image quality of time-of-flight (TOF)-based imaging systems and fluorescence lifetime imaging (FLIM). In this work, we evaluate the gain, detection efficiency, and timing performance of avalanche photodiodes (APD) with photon trapping nanostructures for photons with 450 and 850 nm wavelengths. At 850 nm wavelength, our photon trapping avalanche photodiodes showed 30 times higher gain, an increase from 16% to >60% enhanced absorption efficiency, and a 50% reduction in the full width at half maximum (FWHM) pulse response time close to the breakdown voltage. At 450 nm wavelength, the external quantum efficiency increased from 54% to 82%, while the gain was enhanced more than 20-fold. Therefore, silicon APDs with photon trapping structures exhibited a dramatic increase in absorption compared to control devices. Results suggest very thin devices with fast timing properties and high absorption between the near-ultraviolet and the near infrared region can be manufactured for high-speed applications in biomedical imaging. This study paves the way towards obtaining single photon detectors with photon trapping structures with gains above 10^6 for the entire visible range