Multicolor Photodiode Array for Broad Spectral Detection
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Solution Overview
Problem
Current solid-state imaging devices, particularly CCD technology, are limited in spectral range detection below 1 μm due to silicon absorption, and lack high efficiency and broad spectral response, which is essential for applications like free space laser communication and multicolor imaging.
Innovation Solution
A monolithic photodiode array with InGaAs absorption layers on InP or GaAs substrates, designed for broad spectral detection from UV to 1700 nm or 2500 nm, featuring high quantum efficiency (>90%) and frequency response up to 8 GHz, allowing for independent addressing of each pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CCD technology is used for imaging, then high resolution can be achieved, but the spectral detection range is limited to below 1 μm due to silicon absorption
Solution Approach 1:
The patent employs a multicolor photodiode array with multiple semiconductor layers having different bandgap energies. Each layer is composed of materials optimized for specific wavelength ranges (e.g., Si for visible, InGaAs for infrared), creating a composite structure that detects a broad spectral range from UV to infrared simultaneously within a single device.
2Reliability
If photodiodes are designed for high quantum efficiency, then detection sensitivity improves, but frequency response bandwidth is reduced
Solution Approach 1:
The patent implements different layer thicknesses and doping concentrations at different depths within the photodiode structure. The absorption layers are optimized locally for either high quantum efficiency (thicker, lightly doped regions) or fast response (thinner, heavily doped regions), allowing the device to achieve both high sensitivity and high-speed operation simultaneously through spatially differentiated properties.
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 solution enables broad spectral detection with high quantum efficiency and frequency response, suitable for multicolor imaging and communication applications, overcoming the limitations of existing CCD technology.
Implementation Method 1
A monolithic photodiode array with InGaAs absorption layers on InP or GaAs substrates, designed for broad spectral detection from UV to 1700 nm or 2500 nm
Data Source
AI summary
Novel structures of the photodetector having broad spectral ranges detection capability are provided. The photodetector offers high quantum efficiency>95% over wide spectral ranges, high frequency response>10 GHz (@3 dB). The photodiode array of N×N (or M×N) elements is also provided. The array also offers wide spectral detection ranges ultraviolet to 2500 nm with high quantum efficiency>95% and high frequency response of >10 GHz, cross-talk of <0.1%. In the array, each photodiode is independently addressable and is made either as top-illuminated or as bottom illuminated type detector. The photodiode and its array provided in this invention, could be used in multiple purpose applications such as telecommunication, imaging, and sensing applications including surveillance, satellite tracking, advanced lidar systems, etc. The advantages of this photodetectors are that they are uncooled and performance will not be degraded under wide range of temperature variation.