APD Pixel Layout for Cleaner Near-Range LiDAR Detection
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Solution Overview
Problem
Lidar devices have lower measurement accuracy for objects near to the device compared to objects far away due to the inclusion of unnecessary-carrier-caused signals in distance measurements.
Innovation Solution
The implementation of an avalanche photodiode (APD) array with pixel regions and neighboring regions on a semiconductor substrate, where the APD array includes first and second discharge electrodes and absorption regions to differentiate and discharge necessary and unnecessary carriers, reducing the inclusion of unnecessary-carrier-caused signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single absorption region and single discharge electrode are used per pixel, then the device complexity is reduced, but measurement precision deteriorates due to inability to separate necessary carriers from unnecessary carriers
Solution Approach 1:
The photodetection element is segmented into multiple absorption regions (first absorption region and second absorption region) with corresponding discharge electrodes (first discharge electrode and second discharge electrode). This segmentation allows separate collection of necessary carriers (from pixel region) and unnecessary carriers (from pixel neighboring region), resolving the contradiction by enabling measurement precision improvement through structural segmentation.
Solution Approach 2:
Different regions of the photodetection element are assigned different functions: the first absorption region is optimized for collecting necessary carriers from the pixel region, while the second absorption region collects unnecessary carriers from the pixel neighboring region. This local quality differentiation enables precise separation of carrier signals, improving measurement accuracy without requiring complete redesign of the entire device.
2Measurement precision
If carriers from pixel neighboring region are not separated, then the device complexity remains low, but measurement precision deteriorates due to inclusion of unnecessary carrier signals
Solution Approach 1:
The discharge electrode structure is segmented into first discharge electrode and second discharge electrode, each connected to separate absorption regions. This segmentation creates distinct signal collection paths that physically separate necessary carriers from unnecessary carriers, achieving signal purity improvement through electrode segmentation.
Solution Approach 2:
The second absorption region and second discharge electrode are specifically designed to extract and remove unnecessary carriers generated in the pixel neighboring region from the measurement signal. This extraction mechanism eliminates harmful carrier signals while preserving necessary carriers, resolving the contradiction between signal purity and device complexity.
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 improves the measurement accuracy of the lidar device by reducing unnecessary-carrier-caused signals, especially when receiving light reflected from objects near the device, thereby enhancing the precision of distance measurements.
Implementation Method 1
at least one pixel region formed in a semiconductor substrate and configured to internally generate an electron and a hole in accordance with incident light
Implementation Method 2
a first absorption region formed in the pixel region and configured to absorb a first discharge carrier
Data Source
AI summary
A photodetection element includes a pixel region, a first absorption region, a first discharge electrode, a pixel neighboring region, a second absorption region, and a second discharge electrode. The pixel region is formed in a semiconductor substrate and internally generates an electron and a hole in accordance with the incident light. The pixel neighboring region is formed so as to be adjacent to the pixel region and internally generates an electron and a hole in accordance with the incident light. The second absorption region is formed in the pixel neighboring region and absorbs, of either of the electron and the hole generated in the pixel neighboring region, the carrier equal to a first discharge carrier as a second discharge carrier. The second discharge electrode is formed on the semiconductor substrate and discharges, from the second absorption region, the second discharge carrier absorbed in the second absorption region.