Light Detector Structure for Deep Depletion and Fast TOF Sensing
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Solution Overview
Problem
Current light detectors face challenges in enhancing responsivity, particularly in extending the depletion layer to improve detection speed and accuracy, especially in applications like time-of-flight lidar devices where precise timing is critical.
Innovation Solution
The light detector design incorporates a semiconductor layer with specific conductivity types and impurity concentrations, including a third semiconductor region that facilitates the extension of the depletion layer deeper into the fourth semiconductor region, combined with a structure part having a different refractive index to enhance light concentration and reduce crosstalk noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the depletion layer is extended deeper into the semiconductor layer to improve detection accuracy, then measurement precision is improved, but the time to detect generated charges increases
Solution Approach 1:
The patent applies local quality by creating regions with different impurity concentrations within the semiconductor layer. Specifically, it introduces a fourth semiconductor region with lower first-conductivity-type impurity concentration than the main semiconductor layer, which allows the depletion layer to extend deeper into this region. This localized modification enables extended detection depth without proportionally increasing the overall charge collection time, as the lower impurity concentration region facilitates faster charge drift velocity.
Solution Approach 2:
The patent changes the impurity concentration parameter of the semiconductor material to optimize performance. By setting the first-conductivity-type impurity concentration of the fourth semiconductor region to be lower than that of the main semiconductor layer, the patent creates an optimal balance between depletion layer extension and charge detection speed. This parameter modification allows the electric field to penetrate deeper while maintaining efficient charge collection.
2Measurement precision
If multiple semiconductor regions with alternating conductivity types are introduced to extend the depletion layer, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the semiconductor layer into multiple regions with alternating conductivity types (first semiconductor region of second conductivity type, second semiconductor region of first conductivity type, third semiconductor region of second conductivity type, and fourth semiconductor region of first conductivity type). This segmentation creates a structured approach to extending the depletion layer, where each region serves a specific function in the charge detection process while maintaining overall system organization.
Solution Approach 2:
The patent uses composite semiconductor structures with alternating conductivity types to achieve the desired depletion layer extension. By combining regions of different conductivity types in a systematic arrangement, the patent creates a composite semiconductor structure that optimizes both detection precision and manages complexity through organized heterogeneity.
3Reliability
If a structure part with different refractive index is added to concentrate light, then responsivity is improved, but device complexity increases
Solution Approach 1:
The patent introduces a structure part with a refractive index different from both the semiconductor layer and the surrounding medium as an intermediary optical element. This structure part, positioned between the incident light source and the semiconductor layer, serves as a mediator to concentrate and direct light onto the light-receiving element. The refractive index mismatch enables optical concentration without requiring complex optical systems, thereby improving responsivity while adding minimal structural 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 responsivity of the light detector by shortening the time to detect generated charges as currents, reducing crosstalk noise, and enhancing the accuracy of time-of-flight measurements in lidar systems.
Implementation Method 1
a light detector that detects light incident on a semiconductor region
Implementation Method 2
a structure part having a different refractive index to enhance light concentration
Data Source
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AI summary
A light detector (101) includes a semiconductor layer (21) and a light-receiving element (10). The semiconductor layer (21) is of a first conductivity type. The light-receiving element (10) includes a first semiconductor region (11), a second semiconductor region (12), a third semiconductor region (13), and a fourth semiconductor region (14). The first semiconductor region (11) is of a second conductivity type. The second semiconductor region (12) is located between the first semiconductor region (11) and the semiconductor layer (21). The second semiconductor region (12) is of the first conductivity type and contacts the first semiconductor region (11). The third semiconductor region (13) is located between the second semiconductor region (12) and the semiconductor layer (21). The third semiconductor region (13) is of the second conductivity type. The fourth semiconductor region (14) is located between the third semiconductor region (13) and the semiconductor layer (21). The fourth semiconductor region (14) is of the first conductivity type, and has a lower first-conductivity-type impurity concentration than a first-conductivity-type impurity concentration of the semiconductor layer (21).