Multi-Depletion Single Photon Avalanche Diode for Voltage Adaptability
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Solution Overview
Problem
Existing single photon avalanche diodes (SPADs) have limited operational voltages, which restricts their detection sensitivity and application in various environments.
Innovation Solution
The development of a single photon avalanche diode with multiple depletion regions, allowing for multiple operational voltages, is achieved by vertically stacking junction structures with different breakdown voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single photon avalanche diode uses a conventional single depletion region structure, then the device structure is simple, but the operational voltage range is limited and detection sensitivity is restricted
Solution Approach 1:
The single depletion region is segmented into multiple depletion regions with different breakdown voltages. Each depletion region is formed by vertically stacked PN junctions at different depths, allowing the SPAD to operate at multiple voltage levels and detect photons with different energies, thereby expanding the operational voltage range without creating a completely new device architecture
Solution Approach 2:
The patent transitions from a single-layer depletion region to a vertically stacked multi-layer structure. By arranging PN junctions at different vertical depths, the device gains an additional spatial dimension for voltage control, enabling multiple operational modes within a compact footprint while maintaining structural integration
2Measurement precision
If multiple depletion regions with different breakdown voltages are vertically stacked, then multiple operational voltages and improved detection sensitivity are achieved, but the device structure becomes more complex
Solution Approach 1:
The vertically stacked PN junction structure serves multiple functions simultaneously: each junction acts as an independent photon detection unit with its own breakdown voltage, while collectively forming an integrated SPAD device. This multi-functional design enables the same structural framework to provide both structural support and multiple detection channels, reducing the need for additional separate components
Solution Approach 2:
The patent implements a nested structure where smaller depletion regions are vertically positioned within or alongside larger depletion regions. The PN junctions are arranged in a nested vertical configuration where deeper junctions are surrounded by shallower ones, allowing compact integration of multiple detection zones while maintaining electrical independence through selective biasing
3Adaptability or versatility
If PN junctions are vertically spaced at different depths, then multi-operational voltages are enabled, but the manufacturing precision requirements increase
Solution Approach 1:
The patent varies the vertical spacing parameters between PN junctions to create distinct depletion regions. By controlling the depth and spacing of each junction during fabrication, the design achieves different breakdown voltages for each region. This parameter-based differentiation allows tuning of operational characteristics without changing the fundamental device architecture or requiring post-fabrication adjustments
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 enhances the detection sensitivity of the SPAD across various environments and expands its application fields by providing multiple operational voltages corresponding to the number of depletion regions.
Implementation Method 1
The first diode includes a first PN junction vertically spaced from a light-receiving surface by a first depth. The second diode includes a second PN junction vertically spaced from the light-receiving surface by a second depth greater than the first depth. The third diode includes a third PN junction spaced from the light-receiving surface by a third depth greater than the second depth.
Implementation Method 2
A single photo avalanche diode (SPAD) manufactured by a CMOS process technology has been widely studied and developed. A reaction needs to be generated as soon as the light is received by a light-receiving element. Thus, a photoelectric transformation element having a high sensitivity is desired.
Implementation Method 3
The first to third diodes have different breakdown voltages. The junction structures may be vertically overlapped with each other to form the single photon avalanche diode including multi-depletion regions. Therefore, the single photon avalanche diode may have multi operational voltages corresponding to numbers of the multi-depletion regions.
Data Source
AI summary
A single photon avalanche diode may include a first diode, a second diode and a third diode. The first diode includes a first PN junction vertically spaced from a light-receiving surface by a first depth. The second diode is formed to be partially contacted with the first diode. The second diode includes a second PN junction vertically spaced from the light-receiving surface by a second depth greater than the first depth. The third diode is formed to be partially contacted with the second diode. The third diode includes a third PN junction spaced from the light-receiving surface by a third depth greater than the second depth. The first to third diodes include different breakdown voltages.