Mixed Silicon Germanium APD Matrix for Broad Wavelength Sensitivity
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Solution Overview
Problem
Conventional silicon avalanche photodiode-based light-receiving devices have low sensitivity to long-wavelength light, and increasing the semiconductor material to detect long-wavelength light results in higher costs.
Innovation Solution
A light-receiving device is designed with both silicon and germanium avalanche photodiodes connected in series and parallel, utilizing a silicon semiconductor substrate, allowing for high sensitivity to long-wavelength light while maintaining lower costs by using a standard silicon substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If silicon avalanche photodiodes are used, then the device cost is low, but the sensitivity to long-wavelength light is poor
Solution Approach 1:
The light-receiving device is divided into multiple pixel units, each containing both silicon APD pixels and germanium APD pixels. This segmentation allows different material types to be distributed across the device area, enabling simultaneous detection of short-wavelength (silicon) and long-wavelength (germanium) light without requiring a single expensive homogeneous structure.
Solution Approach 2:
Different regions of the device use different semiconductor materials optimized for different wavelength ranges. Silicon APD pixels are used for short-wavelength detection where silicon has high quantum efficiency, while germanium APD pixels are used for long-wavelength detection where germanium's smaller bandgap provides superior sensitivity. This local optimization resolves the contradiction by matching material properties to wavelength requirements.
2Measurement precision
If germanium avalanche photodiodes are used to detect long-wavelength light, then the sensitivity is high, but the device cost increases
Solution Approach 1:
Instead of using germanium material throughout the entire device, the invention segments the pixel array to include only germanium APD pixels in regions where long-wavelength detection is required. This partial use of germanium material significantly reduces the overall device cost compared to a full germanium implementation, while still achieving high sensitivity for long-wavelength light in the necessary spectral range.
Solution Approach 2:
Germanium material is applied locally only where long-wavelength detection capability is needed, rather than uniformly across the entire device. This localized material deployment minimizes the quantity of expensive germanium material required, thereby reducing device cost while maintaining high sensitivity performance for long-wavelength applications.
3Adaptability or versatility
If a mixed material structure is used, then the wavelength detection range is broad, but the device complexity increases
Solution Approach 1:
The device is segmented into independent pixel units that can be systematically arranged in a regular pattern. Each pixel unit contains both silicon and germanium APD pixels, creating a modular structure that broadens the overall wavelength detection range while maintaining manageable device complexity through repetition of the same basic unit.
Solution Approach 2:
Silicon APD pixels and germanium APD pixels are merged within the same pixel unit and connected to common readout circuitry. This merging approach allows the device to detect both short-wavelength and long-wavelength light simultaneously through a unified structure, reducing complexity compared to having separate detection systems for different wavelength ranges.
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 device achieves high sensitivity across broad wavelength ranges, enabling long-distance measurements with uniform sensitivity characteristics and cost-effective production by leveraging the sensitivity of both silicon and germanium photodiodes in a matrix layout.
Implementation Method 1
The light-receiving device measures the number of incident photons using the APDs
Implementation Method 2
a plurality of first serial connections each of which includes a first avalanche photodiode (APD) and a first resistor connected in series
Data Source
AI summary
A light-receiving device includes a silicon semiconductor substrate, a plurality of first serial connections each of which includes a first avalanche photodiode (APD) and a first resistor connected in series, and a plurality of second serial connections each of which includes a second avalanche photodiode (APD) and a second resistor connected in series. The first APDs and the first resistors are formed on the silicon semiconductor substrate, and the first APDs is formed of silicon. The second APDs and the second resistors are formed on the silicon semiconductor substrate, and the second APDs is formed of a material having a smaller band gap than silicon. The plurality of first and second serial connections is connected in parallel between an anode terminal and a cathode terminal.