SPAD Sensitivity Control Using a Further Depletion Region
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Solution Overview
Problem
Single photon avalanche diodes (SPADs) face saturation and pile-up issues in high light conditions, leading to increased current consumption and distortion of timing information, with existing solutions like aperturing and voltage modulation being inflexible and limited in effectiveness.
Innovation Solution
The implementation of additional contact regions within the diode structure to generate further depletion regions, which steer charge out of the main well, reducing the number of carriers causing avalanches and thus controlling sensitivity by selectively coupling these regions to a regulated supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional contact regions are added to control sensitivity, then saturation and pile-up effects are reduced, but device complexity increases
Solution Approach 1:
The diode structure is segmented into multiple functional regions: a first contact region coupled to the first doped structure, a second contact region coupled to the second doped structure, and additional contact regions coupled to further doped structures. Each segment independently controls charge carrier flow, allowing sensitivity adjustment without requiring complete redesign of the entire device.
Solution Approach 2:
Multiple doped structures are nested within the diode, with each subsequent doped structure contained within or adjacent to previous structures. The first doped structure is nested within the diode, the second doped structure is nested within the first, and further doped structures are nested sequentially, creating a compact multi-layered configuration that reduces overall device footprint.
2Adaptability or versatility
If more doped structures are implemented to create further depletion regions, then sensitivity control is improved, but manufacturing complexity increases
Solution Approach 1:
The invention utilizes parameter changes in the doping process by varying the dopant type (first type vs. second type), doping concentration, and depth for each doped structure. These parameter variations create distinct depletion regions with different characteristics, enabling continuous sensitivity adjustment across a wide range while maintaining compatibility with standard semiconductor manufacturing processes.
Solution Approach 2:
Multiple doped structures serve multiple functions: they create sequential depletion regions for sensitivity control, provide charge carrier collection paths, and enable both photodiode and SPAD operating modes. This multi-functionality reduces the need for separate components and simplifies the overall manufacturing process despite the increased number of doped regions.
3Measurement precision
If the diode operates in SPAD mode with high reverse bias, then single photon detection capability is enhanced, but saturation occurs in high light conditions
Solution Approach 1:
The invention implements dynamic sensitivity control through multiple selectable contact regions that can be selectively coupled to different doped structures. By dynamically switching which contact region is active, the device can adapt its sensitivity level to match the ambient light conditions, maintaining optimal performance across varying illumination levels while preserving single photon detection capability.
Solution Approach 2:
The multi-contact region structure provides feedback mechanisms where the output from different contact regions can be monitored and used to adjust the operating mode. When saturation is detected in high light conditions, the system can switch to utilizing depletion regions formed by other doped structures with appropriate charge steering, effectively providing feedback-based operation mode adjustment.
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 effectively reduces SPAD sensitivity in high light conditions without compromising low light sensitivity, allowing for flexible adjustment between light levels by reducing carrier-induced avalanches and preventing saturation and pile-up effects.
Implementation Method 1
a further doped structure forming a further depletion region within the diode
Implementation Method 2
the further depletion region is configured to steer charge out from the main well of the diode
Implementation Method 3
wherein the further contact structure is selectively coupled to a regulated supply voltage
Implementation Method 4
A photon impinging on a detection region (such as within the depletion region of the PN junction) generate an electron and hole pair via the photoelectric effect
Implementation Method 5
The PN junction is reverse-biased with a voltage magnitude such that when the electron/hole carriers are generated, the electric field applied across the detection region causes the carriers to be accelerated to the anode and cathode
Implementation Method 6
If the kinetic energy of the accelerated carriers is sufficient, additional carriers will be generated from the semiconductor lattice, which are in turn accelerated by the field, and may liberate further carriers in an exponentially increasing fashion
Data Source
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AI summary
A diode, comprising: a first doped structure, doped with a first type of material and forming at least part of an isolation structure for the diode; at least one contact structure located within the first doped structure, the at least one contact structure forming one of the cathode or anode of the diode; a second doped structure, doped with a second type of material, and forming at least one depletion region or PN junction with the first doped structure; at least one second contact structure located within the first doped structure, the at least one second contact structure forming the other of the anode or the cathode of the diode; at least one further contact structure, doped with the first type of material, the at least one further contact structure forming at least one further depletion region or further PN junction, such that the at least one further depletion region is configured to steer charge from the at least one depletion region and thus decrease the sensitivity of the diode.