CQD Photodiode Structure for Long-Range LiDAR Signal Detection
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Solution Overview
Problem
Existing lidar systems face challenges in efficiently detecting poorly reflective objects at long distances and managing the large dynamic range of signal amplitudes, particularly with photodetectors like APDs or SPADs, which are costly and prone to damage from intense laser returns.
Innovation Solution
The integration of colloidal quantum dot (CQD)-based photodetector layers on CMOS readout integrated circuits (ROICs) optimized for nanosecond-scale laser pulses, featuring a photodiode structure with optimized doping and thickness for wide depletion regions and hole/electron collection layers, allowing for efficient absorption and collection of photogenerated charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If APDs or SPADs are used for detecting poorly reflective objects at long distances, then detection capability is improved, but device cost increases and detector becomes prone to damage from intense laser returns
Solution Approach 1:
The patent changes the operational parameters of the photodetector by implementing a dual-gain architecture that switches between high-gain and low-gain modes. This allows the detector to handle both weak signals from poorly reflective objects and strong signals from highly reflective objects without damage, resolving the contradiction between detection capability and susceptibility to damage.
Solution Approach 2:
The patent introduces dynamic gain switching capability where the photodetector can adaptively change its sensitivity level based on the intensity of the incoming signal. This dynamic adjustment prevents detector damage from intense laser returns while maintaining high detection capability for weak signals, eliminating the need for protective measures that would reduce detection performance.
2Reliability
If photodetector arrays are separately fabricated and hybridized to ROICs, then detector performance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the photodetector array fabrication with the ROIC fabrication into a single integrated process. Both the photodetector array and ROIC are fabricated on the same semiconductor substrate using compatible processing steps, eliminating the need for separate fabrication and hybridization. This reduces manufacturing complexity while maintaining detector performance through direct integration.
Solution Approach 2:
The patent develops a universal fabrication process that can produce both photodetector arrays and ROICs using the same manufacturing steps and equipment. This multi-functional approach allows a single fabrication line to produce complete integrated units, reducing the need for multiple specialized manufacturing processes and simplifying production.
3Measurement precision
If photodetectors are optimized for continuous-wave signals over long exposures, then measurement precision is improved, but response speed to nanosecond-scale laser pulses deteriorates
Solution Approach 1:
The patent implements dynamic optimization where the photodetector parameters can be adjusted based on the application requirements. The device can switch between modes optimized for continuous-wave signals (with longer integration times for precision) and modes optimized for nanosecond-scale pulses (with faster response times), allowing both measurement precision and response speed to be optimized for their respective applications.
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 enables fast response to laser pulses, efficient absorption of infrared light, and effective collection of photogenerated charges, reducing the need for high laser energy and minimizing detector damage, while supporting coherent lidar operations for three-dimensional imaging.
Implementation Method 1
colloidal quantum dot (CQD)-based photo-detector layers formed on circuitry... efficient absorption of infrared light and collection of photogenerated charges
Data Source
AI summary
Methods and apparatus for a sensor having a photodetector array having photodetectors comprising a colloidal quantum dot (CQD) structure formed on an integrated circuit. The sensor may comprise a LIDAR time of flight sensor.