GeSi-Silicon Photodiode Array for Visible and NIR Sensing
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Solution Overview
Problem
Conventional silicon-based photodiodes have low optical absorption efficiency for near-infrared wavelengths, limiting their ability to detect a wide range of light spectra and resulting in reduced sensitivity and depth resolution in applications like time-of-flight imaging.
Innovation Solution
Integrating germanium or germanium-silicon photodiodes with silicon photodiodes on a common substrate to create a photodiode array that can detect visible and near-infrared wavelengths, enhancing the device's speed, sensitivity, and dynamic range, and allowing for improved depth resolution in time-of-flight applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon-based photodiodes are used, then the device structure is simple and manufacturing is easy, but the optical absorption efficiency for near-infrared wavelengths is low
Solution Approach 1:
The patent employs a composite material structure consisting of a silicon substrate with a germanium-silicon (GeSi) layer formed on its surface. The GeSi layer has intermediate properties between pure silicon and pure germanium, providing enhanced optical absorption efficiency for near-infrared wavelengths while maintaining compatibility with silicon-based manufacturing processes. This composite approach resolves the contradiction by combining materials to achieve both ease of manufacture and high optical absorption efficiency.
2Reliability
If germanium photodiodes are used to increase optical absorption efficiency for near-infrared wavelengths, then the sensitivity and dynamic range improve, but the device complexity increases
Solution Approach 1:
The patent divides the photodiode structure into distinct functional segments: a silicon substrate providing mechanical support and basic photodetection, and a germanium-silicon layer specifically engineered to enhance near-infrared absorption. This segmentation allows each layer to be optimized for its specific function while maintaining overall device manageability. The GeSi layer is formed as a separate structure on the silicon substrate, enabling independent optimization of thickness and composition to achieve high sensitivity without excessive complexity.
3Adaptability or versatility
If a hybrid photodiode array integrating silicon and germanium-silicon is used, then the operating wavelength range increases, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies local quality by forming germanium-silicon layers selectively at specific locations on the silicon substrate where near-infrared detection is required. Rather than converting the entire substrate to germanium-silicon, the GeSi regions are locally introduced to provide enhanced optical absorption only where needed. This localized approach enables the photodiode array to detect both visible and near-infrared wavelengths while keeping the overall manufacturing process manageable by limiting the complexity to specific device regions.
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
The hybrid photodiode array achieves higher optical absorption efficiency across a broader spectrum, reducing crosstalk and enabling smaller pixel sizes, improved signal-to-noise ratio, and increased depth resolution while maintaining power efficiency.
Implementation Method 1
a semiconductor layer configured to absorb photons at visible wavelengths and to generate photo-carriers from the absorbed photons
Implementation Method 2
the germanium-silicon region configured to absorb photons at infrared or near-infrared wavelengths and to generate photo-carriers from the absorbed photons
Data Source
AI summary
A method for fabricating an image sensor array having a first group of photodiodes for detecting light at visible wavelengths a second group of photodiodes for detecting light at infrared or near-infrared wavelengths, the method including growing a germanium-silicon layer on a semiconductor donor wafer; defining pixels of the image sensor array on the germanium-silicon layer; defining a first interconnect layer on the germanium-silicon layer, wherein the interconnect layer includes a plurality of interconnects coupled to the first group of photodiodes and the second group of photodiodes; defining integrated circuitry for controlling the pixels of the image sensor array on a semiconductor carrier wafer; defining a second interconnect layer on the semiconductor carrier wafer, wherein the second interconnect layer includes a plurality of interconnects coupled to the integrated circuitry; and bonding the first interconnect layer with the second interconnect layer.