Dual-Switch GeSi Photodiode for High-Speed ToF Depth Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photodiodes using silicon as an absorption material for near-infrared wavelengths suffer from slow photo-carrier generation and limited operation speed due to inefficient absorption, which affects depth resolution in time-of-flight applications.
Innovation Solution
The use of a dual-switch photodiode with a germanium-silicon (GeSi) absorption layer and p- and n-doped regions, where two groups of switches collect photo-carriers at different optical phases, enhancing operation speed and depth resolution by utilizing the efficient absorption properties of germanium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If silicon is used as an absorption material for near-infrared wavelengths, then the device structure is simple and manufacturing is easier, but photo-carrier generation is slow and operation speed is limited
Solution Approach 1:
The patent employs a composite material structure consisting of a silicon substrate with a germanium-silicon (GeSi) absorption layer formed on top. The GeSi layer has higher absorption efficiency for near-infrared wavelengths compared to pure silicon, enabling faster photo-carrier generation. This composite approach combines the manufacturing advantages of silicon with the superior optical properties of germanium-silicon, resolving the contradiction between speed and ease of manufacture.
Solution Approach 2:
The patent changes the material composition parameter by introducing germanium into the silicon lattice to form GeSi alloys with varying germanium concentrations (e.g., 10-30% Ge). This parameter change optimizes the absorption coefficient for near-infrared wavelengths while maintaining compatibility with silicon-based manufacturing processes, thereby improving photo-carrier generation speed without excessively complicating manufacturing.
2Measurement precision
If a single photodiode structure is used, then the device complexity is low, but depth resolution in time-of-flight applications is limited
Solution Approach 1:
The patent segments the photodiode structure into multiple functional regions: a silicon substrate, a GeSi absorption layer, p-doped regions, n-doped regions, and dual switch structures. This segmentation allows each region to perform its specific function optimally, with the GeSi layer absorbing photons efficiently and the dual switches enabling phase information extraction, thereby achieving high depth resolution through a segmented architecture.
Solution Approach 2:
The patent introduces a temporal dimension by using dual switches that operate at different phases of the modulation cycle. Instead of merely detecting light intensity, the photodiode structure captures phase information by collecting photo-carriers during different time windows corresponding to different optical phases. This dimensional addition enables precise depth measurement in time-of-flight applications.
3Measurement precision
If higher modulation frequencies are used to improve depth resolution, then the signal-to-noise ratio may deteriorate, but depth resolution improves
Solution Approach 1:
The patent changes the material absorption parameter by using GeSi with higher absorption efficiency, which increases the photo-carrier generation rate. This parameter change allows the system to maintain a strong signal even at higher modulation frequencies, thereby improving depth resolution without sacrificing signal-to-noise ratio. The enhanced absorption ensures sufficient signal strength is generated to overcome noise at elevated frequencies.
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 signal-to-noise ratio and increases depth resolution in time-of-flight systems while maintaining power consumption, allowing for higher modulation frequencies and better material composition analysis.
Implementation Method 1
a germanium-silicon layer coupled to the semiconductor substrate, the germanium-silicon layer including a photodiode region configured to absorb photons and to generate photo-carriers from the absorbed photons
Data Source
AI summary
An apparatus including a semiconductor substrate; an absorption layer coupled to the semiconductor substrate, the absorption layer including a photodiode region configured to absorb photons and to generate photo-carriers from the absorbed photons; one or more first switches controlled by a first control signal, the one or more first switches configured to collect at least a portion of the photo-carriers based on the first control signal; and one or more second switches controlled by a second control signal, the one or more second switches configured to collect at least a portion of the photo-carriers based on the second control signal, where the second control signal is different from the first control signal.