Microstructured Silicon Photodiodes for High-Speed 850 Nm Absorption
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Solution Overview
Problem
Conventional silicon photodetectors face limitations in detecting longer wavelengths and achieving high bandwidth due to the material's transparency and high multiplication noise in other materials like Germanium and InGaAs.
Innovation Solution
The development of a photodetector with microstructure-enhanced photoabsorption, featuring a semiconductor region with microstructures that increase photon absorption at various wavelengths, including those beyond 850 nm, by utilizing resonance, scattering, and near-field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the absorption region is increased to detect longer wavelengths, then quantum efficiency is improved, but bandwidth decreases
Solution Approach 1:
The absorption region is segmented into multiple discrete microstructures (pillars, holes, or voids) arranged in arrays. This segmentation increases the effective absorption path length through light trapping effects while maintaining a thin overall device structure, thereby achieving high quantum efficiency without sacrificing bandwidth
Solution Approach 2:
The invention transitions from a planar absorption region to a three-dimensional microstructured absorption region. The microstructures extend into the vertical dimension with optimized heights and spacing, creating multiple reflection and absorption opportunities that enhance quantum efficiency while keeping the lateral footprint compact and response time short
2Measurement precision
If other materials like Germanium or InGaAs are used to detect longer wavelengths, then detection capability is improved, but multiplication noise increases
Solution Approach 1:
The invention changes the optical parameters of silicon by introducing microstructures that modify light propagation and absorption characteristics. This enables silicon to effectively detect longer wavelengths (beyond 850 nm) that it would normally be transparent to, while maintaining silicon's inherent low multiplication noise advantage
Solution Approach 2:
The device creates a composite structure combining silicon material with microarchitectural features (pillars, holes, voids). This composite approach leverages silicon's low noise properties while the microstructural geometry provides enhanced absorption for longer wavelengths, achieving a balance between detection capability and noise performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances quantum efficiency to at least 60% and achieves data bandwidths greater than 5 Gb/s at 850 nm, with potential for even higher bandwidths and efficiencies across a broader spectral range.
Implementation Method 1
by utilizing resonance, scattering, and near-field effects
Implementation Method 2
by utilizing resonance, scattering, and near-field effects
Implementation Method 3
by utilizing resonance, scattering, and near-field effects
Implementation Method 4
a photodetector with microstructure-enhanced photoabsorption... configured to convert optical energy to electrical energy
Data Source
AI summary
Techniques for enhancing the absorption of photons in semiconductors with the use of microstructures are described. The microstructures, such as pillars and/or holes, effectively increase the effective absorption length resulting in a greater absorption of the photons. Using microstructures for absorption enhancement for silicon photodiodes and silicon avalanche photodiodes can result in bandwidths in excess of 10 Gb/s at photons with wavelengths of 850 nm, and with quantum efficiencies of approximately 90% or more.