Quantum Dot Photodetector Interlayer for Dark Current Suppression
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Solution Overview
Problem
The dark current in photodetector elements with quantum dot layers increases after the formation of an optical filter, leading to a reduced signal-to-noise ratio.
Innovation Solution
A photodetector element is designed with a quantum dot layer, an optical filter, and an interlayer between the quantum dot layer and the optical filter. The interlayer includes atoms like Si, Al, Zr, Sn, Zn, Ce, and Hf, or a paraxylene polymer, to suppress dark current and maintain external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical filter is formed on a photoelectric conversion element using quantum dots, then the spectral selectivity is improved, but the dark current increases
Solution Approach 1:
An interlayer comprising silicon oxide, silicon oxynitride, silicon nitride, zirconium oxide, zinc oxide, cerium oxide, aluminum oxide, or hafnium oxide is introduced between the quantum dot layer and the optical filter. This intermediary layer prevents direct contact between the optical filter and quantum dots, thereby suppressing dark current generation while maintaining the spectral filtering function.
Solution Approach 2:
The patent employs composite material structures including multiple oxide layers (e.g., silicon oxide combined with silicon nitride) to achieve both protective and functional properties. The composite interlayer structure provides enhanced suppression of dark current while maintaining optical transparency and structural integrity.
2Measurement precision
If an optical filter is formed on a photoelectric conversion element using quantum dots, then the wavelength filtering is improved, but the signal-to-noise ratio decreases
Solution Approach 1:
The interlayer acts as a protective mediator that prevents the optical filter from directly interacting with the quantum dot layer, thereby reducing noise generation while preserving the wavelength filtering capability. This maintains signal integrity by preventing dark current-induced noise.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of the interlayer to achieve the right balance between protection and optical performance. By controlling the physical and chemical parameters of the interlayer materials, the system maintains high signal-to-noise ratio while achieving effective wavelength filtering.
3Object-generated harmful factors
If an interlayer is added between the quantum dot layer and optical filter, then the dark current is suppressed, but the device complexity increases
Solution Approach 1:
The interlayer is designed with optimized thickness parameters (typically nanometer-scale) and selected from a limited range of compatible oxide materials that can be deposited using standard thin-film techniques. This parameter optimization minimizes the added complexity while achieving effective dark current suppression.
Solution Approach 2:
The patent uses composite oxide materials that can be formed using conventional semiconductor fabrication processes such as atomic layer deposition (ALD) or chemical vapor deposition (CVD). These materials are compatible with existing manufacturing workflows, thereby limiting the increase in device 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
The proposed configuration effectively suppresses the increase in dark current and maintains a high sensitivity of the photodetector element, improving its accuracy in infrared sensing.
Implementation Method 1
A substance reduced to about several nm to ten and several nm exhibits physical properties different from those in a bulk state. Such a phenomenon is called a quantum size effect or the like
Implementation Method 2
research on the quantum dot has advanced. For example, a use of the quantum dot as a material for a photoelectric conversion element is being studied
Implementation Method 3
an optical filter provided on a light incident side of the photoelectric conversion element
Data Source
AI summary
Provided is a photodetector element having a photoelectric conversion element, an optical filter provided on a light incident side of the photoelectric conversion element, and an interlayer provided between the photoelectric conversion element and the optical filter, in which the photoelectric conversion element has a quantum dot layer, a first electrode, and a second electrode, the optical filter has predetermined spectral characteristics, and the interlayer includes at least one kind of atom selected from the group consisting of Si, Al, Zr, Sn, Zn, Ce, and Hf, or includes a paraxylene polymer, or has a water vapor permeability as determined by a method in accordance with JIS K 7129 of 1×10−4 g/m2/day or less. Provided also are an image sensor and a method for manufacturing a photodetector element.