Photodiode Array Overlapping Electrodes and Curvilinear Resistive Layer
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Solution Overview
Problem
Conventional photodiode arrays struggle with pulse separation when multiple photons are incident at short intervals, leading to a shortened interval between output pulse signals and an inability to perform effective photon counting.
Innovation Solution
The photodiode array design features a second contact electrode positioned overlapping the first contact electrode, minimizing space for the resistive layer connection, omitting wiring in light detecting sections, and using a curvilinear resistive layer with SiCr for high optical transmittance, which increases the aperture ratio and allows longer resistive layer lengths, thereby stabilizing the semiconductor surface and shortening recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional wiring layout is used with separate contact electrodes, then the connection of the resistive layer is simplified, but the aperture ratio of the light detecting sections is reduced due to wiring occupying space
Solution Approach 1:
The patent merges the first contact electrode and second contact electrode into a single overlapping configuration, eliminating the need for separate wiring paths. This integration removes wiring from the light detecting section plane, thereby increasing the aperture ratio while maintaining simplified connection through the overlapping electrode structure
Solution Approach 2:
The patent utilizes the vertical dimension by positioning the first and second contact electrodes in different planes (overlapping configuration). This three-dimensional arrangement allows the resistive layer to connect between electrodes without requiring lateral wiring space, thus increasing the aperture ratio in the horizontal plane while maintaining electrical connection
2Loss of time
If the resistive layer is made shorter to reduce capacitance, then the recovery time is shortened, but the resistance value decreases which affects quenching performance
Solution Approach 1:
The patent changes the geometric parameters of the resistive layer by extending it in a curvilinear (sinuous) manner. This increases the length and resistance value of the resistive layer without proportionally increasing the capacitance, as the extended path is distributed. The curvilinear extension allows achieving both high resistance value for quenching performance and controlled capacitance for fast recovery time
3Productivity
If multiple photons are detected at short intervals, then the counting rate increases, but the interval between output pulse signals becomes too short to perform pulse separation
Solution Approach 1:
The patent optimizes the RC time constant by adjusting the resistive layer parameters (increasing resistance through curvilinear extension) to achieve faster voltage recovery after avalanche breakdown. This reduced recovery time enables the system to process multiple photons at high counting rates while maintaining sufficient pulse separation, thereby resolving the contradiction between high productivity and time loss
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
This design achieves a high count rate by significantly shortening recovery time and maintaining high detection efficiency even at closer light detecting section intervals, enhancing the dynamic range and photon counting capability.
Implementation Method 1
Because SiCr has high optical transmittance, even when a resistive layer is present in the light detecting sections, incident photons are allowed to transmit through the resistive layer
Implementation Method 2
Carriers generated in the p-n junction by incidence of photons flow in the resistive layer
Implementation Method 3
When the APDs are operated in the Geiger mode, it is possible to detect feeble light (photons). Although an electric current flows in the pixels in which an avalanche effect occurs in the APD
Data Source
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AI summary
[Problem] The present invention provides a high dynamic range photodiode array with a high counting rate. [Means for Solution]A light receiving region includes a plurality of light detecting sections 10, and each of the light detecting sections 10 comprises: a first semiconductor region 12 of a first conductivity type, a second semiconductor region 13, 14 of a second conductivity type, the second semiconductor region forming a p-n junction with the first semiconductor region, a first contact electrode 3A being in contact with the second semiconductor region, a second contact electrode 4A having a material different from that of the first contact electrode 3A, the second contact electrode 4A being arranged at a position overlapping the first contact electrode 3A and being in contact with the first contact electrode, and a resistive layer 4B continued to the second contact electrode 4A.