Unique Hyperspectral Response Design Enabled by Periodic Surface Textures in Photodiodes

Area of Science:

• Photonics
• Materials Science
• Spectroscopy

Background:

• Hyperspectral imaging applications are limited by bulky, complex optical components.
• Existing spectral response devices require intricate filters and dispersion lenses.

Purpose of the Study:

• To propose a novel method for designing engineered spectral responses using photon-trapping surface textures (PTSTs).
• To develop and validate an analytical model for electromagnetic wave coupling with PTSTs.
• To demonstrate the feasibility of PTST-equipped photodiodes for miniaturized hyperspectral imaging.

Main Methods:

• Developed an analytical model for electromagnetic wave coupling using the effective refractive index of silicon with PTSTs.
• Validated the model against simulations and experimental data from PTST-equipped photodiodes fabricated using CMOS-compatible processes.
• Characterized the electrical and optical performance of the fabricated photodiodes.

Main Results:

• Observed a linear relationship between peak coupling wavelength and PTST period, and a proportional relation to PTST diameters.
• Identified a significant correlation between inter-PTST spacing and wave propagation modes.
• Demonstrated high-speed (27 ps), high-gain (M: 90), low-voltage (breakdown voltage: ~8.0 V) performance of PTST photodiodes.

Conclusions:

• PTSTs eliminate the need for external diffraction optics, enabling system miniaturization for hyperspectral imaging.
• The developed model accurately predicts spectral response, facilitating on-chip spectrometer integration.
• These advancements pave the way for cost-effective, real-time hyperspectral imaging systems.