Ultrathin Si-PD design with enhanced guided-mode resonance through slanted surface-relief gratings

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Photodetectors (PDs) often struggle with low sensitivity to near-infrared (NIR) light.
• There's a critical trade-off between absorption layer thickness and high-speed response in PDs.

Purpose of the Study:

• To introduce a new surface-illuminated silicon photodetector (PD) structure.
• To overcome limitations in NIR sensitivity and the thickness-speed trade-off in PDs.

Main Methods:

• Proposed a novel structure featuring a slanted surface-relief grating composed of tilted silicon (Si) and silicon dioxide (SiO2) arrays.
• Utilized a circular resonator shape in the absorption layer to support lateral quasi-propagating modes.
• Employed simulations to validate the design's performance.

Main Results:

• The slanted grating efficiently deflects normally incident photons.
• The design extends photon lifetime, significantly increasing NIR photon absorption.
• Achieved 29.2% absorption at 1012 nm with an ultra-thin 300 nm absorption layer.

Conclusions:

• The innovative PD design enhances NIR light absorption in thin layers.
• This structure offers a pathway to developing thin and high-speed photodetectors.
• The proposed design addresses key challenges in current photodetector technology.