Geiger Mode APD Array Common Contact Pulse Discrimination
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Solution Overview
Problem
Semiconductor photodetector arrays, specifically Geiger-mode avalanche photodiodes, face limitations in spatial resolution due to the need for complex electronics and packaging constraints, which restrict the number of pixels and fill factor, making it difficult to accurately determine the position of photon absorption in applications like Positron Emission Tomography and LIDAR techniques.
Innovation Solution
A multipixel photo detector array with Geiger mode avalanche photodiodes features a common anode and cathode contact configuration, allowing for differentiation of current pulses from each pixel through varying quenching resistor values, enabling discrimination of photon absorption location without independent outputs for each pixel, thus simplifying readout circuitry and increasing the dynamic range and fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each pixel has independent outputs with driving and readout circuits, then spatial information can be obtained, but device complexity and packaging constraints increase, limiting the number of pixels and fill factor
Solution Approach 1:
Multiple pixels share common anode and cathode contacts, merging the readout paths. The patent combines multiple photodiode pixels into a single integrated structure where adjacent pixels share electrical contacts, eliminating the need for separate readout circuits per pixel while maintaining spatial discrimination capabilities through pulse shape analysis
Solution Approach 2:
Each pixel is given a unique local characteristic through different quenching resistor values or capacitor configurations. This local differentiation allows the system to identify which specific pixel detected a photon by analyzing the unique pulse shape characteristics generated by each pixel's distinct electrical properties
2Productivity
If the number of pixels is increased to improve dynamic range, then sensitivity improves, but packaging constraints and fill factor reduction due to individual pixel outputs limit the achievable pixel count
Solution Approach 1:
Adjacent pixels share common anode and cathode contacts, merging electrical paths to reduce the area occupied by interconnect structures. This sharing approach minimizes the non-active area between pixels, thereby increasing the fill factor and allowing more pixels to be packed into a given detector area
Solution Approach 2:
The common anode and cathode contacts serve multiple pixels simultaneously, making these electrical structures multi-functional. A single contact structure performs the function of connecting multiple pixels to the readout system, reducing the overall complexity and area requirements compared to dedicated contacts for each pixel
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 approach allows for accurate spatial information and higher sensitivity in photodetector arrays by enabling discrimination among pixels through distinct current pulse shapes, reducing the need for complex electronics and increasing the number of pixels that can be effectively used, thereby enhancing the dynamic range and fill factor of the array.
Implementation Method 1
At this operating condition, the electric field within the GM-APD depletion layer is high enough that charge carriers injected in this region may trigger a self-sustaining avalanche multiplication process by impact ionization mechanisms
Implementation Method 2
a self-sustaining avalanche multiplication process by impact ionization mechanisms
Implementation Method 3
When a photon is absorbed in the depletion layer of the diode, a photo electron-hole pair is generated
Data Source
AI summary
A multi-pixel photodetector array may include a semiconductor substrate having a back side and a front side, Geiger mode avalanche photodiodes (GM-APDs) on the semiconductor substrate, each including an anode contact, and a common cathode for the GM-APDs and having a first connection lead on the backside of the semiconductor substrate. The multi-pixel photodetector array may include a second connection lead, and a common anode on the front side of the semiconductor substrate and configured to couple in common the anode contacts of the GM-APDs to the second connection lead. Each GM-APD may be configured to generate, when a photon impinges thereon, a current pulse of different shape for discrimination by an external circuit connected to the common cathode and the common anode.