Multiplexed Schottky Photodiode Array for Imaging
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Solution Overview
Problem
Existing multi-pixel detector arrays face challenges in packaging and integration due to the need for individual connections to external circuitry, which reduces the geometrical fill factor and dynamic range, and is costly for large arrays, especially when using techniques like Flip Chip or Bridge Bonding.
Innovation Solution
A multi-pixel photo detector array with a Schottky photodiode structure featuring a distributed anode contact buried in metal-filled trenches, connected to a common anode current collecting grid and shared cathode contact, allowing multiplexing of pixel information through a reduced number of leads, and adaptable trench depth and spacing for unique depletion layer thickness and pinch-off conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If individual connections are provided for each pixel to external circuitry, then each pixel can be individually addressed and read out, but the geometrical fill factor and dynamic range are reduced, and packaging complexity increases
Solution Approach 1:
Multiple pixel anode contacts are merged into a single common anode contact that collects current from all pixels. This combining approach eliminates the need for individual anode connections per pixel, thereby increasing the geometrical fill factor while maintaining individual pixel addressing capability through the shared contact structure.
Solution Approach 2:
The common anode contact serves multiple functions simultaneously: it acts as the current collection point for all pixels, provides a reference potential for the photodiode junctions, and enables individual pixel selection through cathode contact control. This multi-functionality reduces the number of required connections while preserving full addressing capability.
2Loss of information
If individual connections are provided for each pixel, then complete pixel information can be read out, but the number of leads increases and packaging becomes more complex and costly
Solution Approach 1:
The patent merges multiple individual anode connections into a single common anode contact that serves all pixels. This consolidation dramatically reduces the number of leads required for packaging while maintaining the ability to read out information from each pixel individually through the shared contact and pixel-specific cathode controls.
Solution Approach 2:
Instead of providing individual connections in the planar dimension, the patent uses a shared three-dimensional contact structure that collects current from multiple pixels vertically and laterally. This dimensional approach allows multiple pixels to share a single contact point without losing individual addressing capability.
3Ease of operation
If Flip Chip or Bridge Bonding techniques are used for integration, then individual pixel connections are achieved, but the process becomes more complex and costly
Solution Approach 1:
The patent combines multiple pixel anode contacts into a single common contact structure, eliminating the need for complex Flip Chip or Bridge Bonding techniques that would be required to establish individual connections for each pixel. This merging approach simplifies the fabrication process while maintaining individual pixel connectivity through the shared contact.
Solution Approach 2:
The patent extracts the complex individual connection requirement by providing only a common anode contact, removing the need for sophisticated packaging techniques. The individual pixel connection need is satisfied through the shared contact combined with pixel-specific cathode control, thereby extracting and eliminating the complexity of advanced bonding processes.
4Reliability
If the active region thickness is increased to enhance photon detection effectiveness, then sensitivity to long wavelength photons improves, but the device structure becomes more complex
Solution Approach 1:
The patent merges multiple pixels into a shared structure with a common anode contact and individual cathode contacts. This merged architecture allows the active region thickness to be increased for enhanced long wavelength photon detection without proportionally increasing overall device complexity, as the shared contact structure serves multiple pixels simultaneously.
Solution Approach 2:
The common anode contact structure performs multiple functions: it serves as the current collection point for all pixels, provides the reference potential for the photodiode junctions, and enables individual pixel selection. This multi-functionality allows the active region to be optimized for long wavelength detection without adding proportional complexity to the contact 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
This configuration enhances photon detection effectiveness by increasing the active region thickness, reduces the number of leads required, and simplifies driving and readout circuitry, while maintaining high sensitivity and fill factor, especially for long wavelength photons, and allows for simultaneous imaging of multiple wavelengths.
Implementation Method 1
Each illuminated pixel of the pixelated scintillator is detected by a respective photodiode of the detector array that converts the light into electrical signals used for imaging purposes
Implementation Method 2
The thickness of the depleted region of which is adjusted by varying the depth of metal contact trenches in a lightly doped semiconductor epilayer
Data Source
AI summary
A detector array for an imaging system may exploit the different sensitivities of array pixels to an incident flux of low energy photons with a wavelength falling near the high end of the range of sensitivity of the semiconductor. The detector array may provide the de-multiplexable spatial information. The detector array may include a two-terminal multi-pixel array of Schottky photodiodes electrically connected in parallel.