Quantum Dot Photodetectors with Tuned Optical Paths for Infrared Sensitivity
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Solution Overview
Problem
Existing photodetector elements, such as silicon photodiodes and InGaAs-based semiconductors, have low sensitivity in the infrared region and require high-cost processes, limiting their effectiveness in image sensors.
Innovation Solution
A photodetector element with a photoelectric conversion layer containing aggregates of semiconductor quantum dots, where the wavelength and optical path length satisfy specific relationships, enhancing optical interference and improving external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If semiconductor quantum dots are used in the photoelectric conversion layer, then sensitivity in the infrared region is improved, but external quantum efficiency is insufficient
Solution Approach 1:
The patent optimizes the optical path length parameter Lλ to satisfy specific relationships with the wavelength λ of target light (Expression 1: 0.05 + m/2 ≤ Lλ/λ ≤ 0.35 + m/2, where m is an integer). This parameter optimization enables the photodetector to achieve both high sensitivity in the infrared region and high external quantum efficiency by controlling the interaction between light and semiconductor quantum dots through precise optical path length adjustment.
2Reliability
If InGaAs-based semiconductor material is used to achieve high quantum efficiency, then external quantum efficiency is improved, but manufacturing cost increases due to high-cost processes such as epitaxial growth
Solution Approach 1:
The patent replaces expensive InGaAs-based semiconductor materials requiring complex epitaxial growth processes with semiconductor quantum dots that can be manufactured through simpler, lower-cost methods. The quantum dot-based photoelectric conversion layer achieves comparable or superior external quantum efficiency while avoiding the high manufacturing costs associated with traditional infrared photodetector materials and processes.
Solution Approach 2:
The patent changes the material parameter from InGaAs-based semiconductors to semiconductor quantum dots, and optimizes the optical path length parameter Lλ to achieve high external quantum efficiency through a cost-effective manufacturing approach that does not require expensive epitaxial growth processes.
3Ease of manufacture
If silicon photodiode is used, then manufacturing is easier and cost is lower, but sensitivity in the infrared region having a wavelength of 900 nm or more is insufficient
Solution Approach 1:
The patent maintains the manufacturing simplicity and cost-effectiveness of silicon photodiodes while replacing the silicon photoelectric conversion layer with semiconductor quantum dots that are specifically optimized for infrared detection. This substitution preserves the ease of manufacturing through simple layer formation processes while dramatically improving sensitivity in the infrared region with wavelengths of 900 nm or more.
Solution Approach 2:
The patent creates a composite structure combining semiconductor quantum dots with a matrix material to form the photoelectric conversion layer. This composite approach maintains the manufacturing simplicity of traditional photodiode structures while incorporating quantum dot materials that provide enhanced infrared sensitivity, achieving both low-cost manufacturing and high sensitivity performance.
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 photodetector element achieves high external quantum efficiency, particularly in the infrared region, with improved sensitivity and charge transport characteristics.
Implementation Method 1
a photoelectric conversion layer that contains aggregates of semiconductor quantum dots between a first electrode layer and a second electrode layer
Implementation Method 2
a wavelength λ (nm) of target light to be detected by the photodetector element and an optical path length Lλ (nm) of light having the wavelength from a surface of the second electrode layer on a side of the photoelectric conversion layer to a surface of the photoelectric conversion layer on a side of the first electrode layer satisfy a relationship of the following Expression (1)
Data Source
AI summary
A photodetector element includes a photoelectric conversion layer that contains aggregates of semiconductor quantum dots between a first electrode layer and a second electrode layer, where the first electrode layer is provided on a light incident side with respect to the second electrode layer, and a wavelength λ (nm) of target light to be detected by the photodetector element and an optical path length Lλ (nm) of light having the wavelength λ, from a surface of the second electrode layer on a side of the photoelectric conversion layer to a surface of the photoelectric conversion layer on a side of the first electrode layer satisfy a relationship of the following Expression (1). m is an integer of 0 or more.0.05+m/2≤Lλ/λ≤0.35+m/2 (1)