Microstructure Enhanced Silicon Photodetectors for High Bandwidth
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Solution Overview
Problem
Conventional silicon photodetectors face limitations in detecting longer optical wavelengths due to low absorption and high noise, particularly at wavelengths above 800 nm, which restricts their bandwidth and quantum efficiency, making them inadequate for modern telecommunications and data center applications.
Innovation Solution
The development of microstructure-enhanced photodetectors with semiconductor regions featuring pillars, holes, or voids arranged in arrays to increase photon absorption, utilizing resonance, scattering, and near-field effects to enhance absorption coefficients, allowing for higher bandwidth and quantum efficiency at longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the absorption region is increased to improve quantum efficiency at 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 resonance and scattering effects while maintaining a physically thin structure, thereby achieving high quantum efficiency without sacrificing bandwidth.
Solution Approach 2:
The patent transitions from a conventional planar absorption region to a three-dimensional microstructured array. By introducing vertical dimensionality with pillars or holes of controlled depth and spacing, the effective optical path length is extended without increasing the lateral footprint or reducing the electrical bandwidth associated with thinner structures.
2Ease of manufacture
If conventional silicon photodetectors are used for longer wavelengths, then manufacturing simplicity is maintained, but absorption and quantum efficiency deteriorate
Solution Approach 1:
The patent modifies the geometric parameters of the silicon absorption region by introducing microstructures with specific dimensions (pillar diameters, hole sizes, spacing, depths) that are optimized for resonant absorption at target wavelengths. This parameter optimization enhances quantum efficiency while maintaining silicon's manufacturing advantages.
Solution Approach 2:
The patent creates a composite structure combining silicon microstructures with dielectric materials (such as silicon dioxide or silicon nitride) that fill the spaces between pillars or lines. This composite approach enhances optical confinement and absorption while maintaining compatibility with standard semiconductor fabrication processes.
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
These microstructure-enhanced photodetectors achieve quantum efficiencies of over 60% and data bandwidths exceeding 5 Gb/s at 850 nm, and 1 Gb/s at 980 nm, while reducing capacitance, thus overcoming the limitations of conventional silicon photodetectors.
Implementation Method 1
The microstructures increase absorption at least in part by forming an absorbing mode high contrast grating that makes use of resonance effects
Implementation Method 2
The microstructures increase absorption at least in part by forming an absorbing mode high contrast grating that makes use of scattering effects
Implementation Method 3
The microstructures increase absorption at least in part by forming an absorbing mode high contrast grating that makes use of near field effects
Implementation Method 4
The microstructures increase absorption at least in part by forming an absorbing mode high contrast grating that makes use of interference effects
Implementation Method 5
a microstructure-enhanced photon absorbing semiconductor region configured to absorb photons from a source signal
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.