III-V Infrared Image Sensor Structure for Broader Wavelength Response
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Solution Overview
Problem
Existing image sensors, particularly CMOS image sensors, face limitations in detecting infrared wavelengths due to narrower wavelength coverage, lower absorption coefficients, and slower carrier mobility compared to silicon-based p-n junction diodes.
Innovation Solution
The use of III-V compound layers with wide infrared wavelength coverage, high absorption coefficients, and high carrier mobility, combined with transistors and structures like shallow trench isolation and epitaxy layers, enhances the performance of infrared image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon substrates with p-n junction diodes are used in CMOS image sensors, then the device structure and manufacturing process are well-established and reliable, but the infrared wavelength coverage is limited and response speed is reduced
Solution Approach 1:
The patent changes the material parameter from silicon to III-V compound materials (such as InAlGaAs), which fundamentally alters the optical and electrical properties to enable broader infrared wavelength coverage while maintaining manufacturing reliability through established epitaxial growth techniques
Solution Approach 2:
The patent employs composite material structures combining III-V compound layers with silicon substrates, integrating the advantages of both materials: the III-V layer provides superior infrared detection properties while the silicon substrate offers mechanical support and existing CMOS compatibility
2Ease of manufacture
If silicon substrates with p-n junction diodes are used in CMOS image sensors, then the manufacturing process is mature and cost-effective, but the carrier mobility and response speed are limited
Solution Approach 1:
The patent changes the material composition parameter from pure silicon to III-V compound materials, which inherently possess higher carrier mobility due to their material properties, thereby improving response speed while using established epitaxial manufacturing techniques
3Device complexity
If silicon-based sensors are used, then the structure is simple and manufacturing is straightforward, but the absorption coefficient in infrared region is low and light current leakage occurs
Solution Approach 1:
The patent uses composite material structures with III-V compound layers that provide high infrared absorption coefficients, improving detection accuracy while maintaining relatively simple device architecture through epitaxial layer growth
Solution Approach 2:
The patent introduces intermediate layers and structures (such as buffer layers and isolation structures) that mediate between the silicon substrate and the III-V compound layer, enabling effective infrared detection while managing the complexity of the heterogeneous structure
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 III-V compound layers enable wider infrared response, faster pixel response, and improved light detection capabilities, surpassing the limitations of silicon-based sensors.
Implementation Method 1
epitaxially grown using techniques like MBE or MOCVD
Implementation Method 2
photodiode elements and MOS transistors, to collect photo energy to convert images to streams of digital data
Data Source
AI summary
A method includes following steps. A first III-V compound layer is epitaxially grown over a semiconductive substrate. The first III-V compound layer has an energy gap in a gradient distribution. A source/drain contact is formed over the first III-V compound layer. A gate structure is formed over the first III-V compound layer.