Germanium Photodetector Gap Structure for Lower Dark Current
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Solution Overview
Problem
Conventional germanium-based photodetectors embedded in semiconductor substrates face issues with dark current due to crystal defects like slips, which reduce the accuracy of image sensors, especially in Time-of-Flight systems that rely on infrared light.
Innovation Solution
A germanium-based well is embedded in a semiconductor material layer with a gap surrounding its lateral side surfaces, minimizing surface contact with the substrate and reducing crystal defects, thereby reducing dark current and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If germanium-based photodetector is embedded in semiconductor substrate, then infrared light detection capability is improved, but crystal defects like slips occur due to surface contact, worsening measurement precision
Solution Approach 1:
The patent extracts the germanium-based well from direct contact with the semiconductor substrate by introducing a gap around its lateral side surfaces. This separation removes the harmful interaction between the germanium well and substrate that causes crystal defects, while preserving the infrared detection function of the germanium material.
Solution Approach 2:
The gap acts as an intermediary space between the germanium-based well and the semiconductor substrate. This intermediate region prevents direct surface contact and the propagation of crystal defects from the substrate to the germanium well, while still allowing the device to function as intended.
2Measurement precision
If germanium-based well is embedded in semiconductor material, then near-infrared detection efficiency is improved, but dark current increases due to surface contact area, worsening signal quality
Solution Approach 1:
The patent removes the harmful surface contact between the germanium-based well and semiconductor material by creating a gap around the lateral side surfaces. This extraction of the contact interface eliminates the source of dark current generation while preserving the beneficial near-infrared detection capability.
3Device complexity
If germanium-based photodetector contacts semiconductor substrate, then device integration is improved, but quantum efficiency decreases due to crystal defects, worsening detection performance
Solution Approach 1:
The gap serves as an intermediary that prevents direct contact between the germanium-based well and semiconductor substrate. This intermediate space blocks the transmission of crystal defects from the substrate to the germanium well, thereby preserving quantum efficiency while maintaining device integration through the embedded well 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
The approach effectively minimizes crystal defects and dark current, enhancing the accuracy and performance of image sensors by reducing the surface contact area between the germanium-based well and the substrate, leading to improved quantum efficiency in near-infrared light detection.
Implementation Method 1
Germanium-based photodetector with reduced dark current and methods of making the same... near-infrared light detection
Data Source
AI summary
A photodetector including a substrate having a semiconductor material layer, such as a silicon-containing layer, and a germanium-based well embedded in the semiconductor material layer, where a gap is located between a lateral side surface of the germanium-based well and the surrounding semiconductor material layer. The gap between the lateral side surface of the germanium-based well and the surrounding semiconductor material layer may reduce the surface contact area between the germanium-containing material of the well and the surrounding semiconductor material, which may be a silicon-based material. The formation of the gap located between a lateral side surface of the germanium-based well and the surrounding semiconductor material layer may help minimize the formation of crystal defects, such as slips, in the germanium-based well, and thereby reduce the dark current and improve photodetector performance.