  Silicon photodetectors operating at near-infrared wavelengths with high-speed
and high sensitivity are becoming critical for emerging applications, such as
Light Detection and Ranging Systems (LIDAR), quantum communications, and
medical imaging. However, such photodetectors present a bandwidth-absorption
trade-off at those wavelengths that have limited their implementation. Photon
trapping structures address this trade-off by enhancing the light-matter
interactions, but maximizing their performance remains a challenge due to a
multitude of factors influencing their design and fabrication. In this paper,
strategies to improve the photon trapping effect while enhancing the speed of
operation are investigated. By optimizing the design of photon trapping
structures and experimentally integrated them in high-speed photodetectors, a
simultaneous broadband absorption efficiency enhancement up to 1000% and a
capacitance reduction of more than 50% has been achieved. Such work also allows
to present empirical equations to correlate the quantum efficiency of
photodetectors with the physical properties of the photon-trapping structures,
material characteristics, and limitations of the fabrication technologies. The
results obtained, open routes towards designing cost-effective CMOS integrated.
