Plasmonic Photodetector Structure for Sub-Wavelength Light Sensing
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Solution Overview
Problem
Conventional photodetectors face limitations in reducing detector size and pixel size due to direct light absorption, leading to inefficiencies in photoelectric conversion and internal quantum efficiency, especially when incident light is smaller than the wavelength band.
Innovation Solution
The use of surface plasmon polaritons (SPPs) generated at metal-dielectric interfaces, where incident light interacts with a metal layer to create surface plasmons, which are then absorbed by a light absorbing layer, causing charges to tunnel through an insulation film and induce photocurrent, enhancing light sensing capability and quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional photodetectors use direct light absorption in a gate, then photoelectric conversion occurs, but the detector size and pixel size cannot be reduced effectively because incident light is directly absorbed into a gate of smaller size than the wavelength band
Solution Approach 1:
The patent introduces surface plasmon polaritons (SPPs) as an intermediate dimensionality - converting incident light into evanescent waves that can be confined to sub-wavelength scales. The metal layer transforms optical energy into SPPs that propagate along the metal-dielectric interface, enabling effective coupling with sub-wavelength gate structures that would otherwise be too small to absorb light directly.
Solution Approach 2:
The patent uses surface plasmons as an intermediary between incident light and the gate structure. The metal layer converts incident photons into SPPs, which then interact with the gate, enabling photoelectric conversion in structures smaller than the incident light wavelength would normally permit.
2Length of moving object
If the gate size is reduced to decrease detector size, then miniaturization is achieved, but light excitation does not occur because incident light is directly absorbed into a gate of smaller size than the wavelength band
Solution Approach 1:
The patent transforms the interaction from direct optical absorption to SPP-mediated excitation. The metal layer converts incident light into surface plasmon polaritons that can effectively couple with sub-wavelength gate structures, enabling light excitation in miniaturized gates that would otherwise be ineffective.
Solution Approach 2:
The patent changes the energy transfer mechanism from direct photon absorption to SPP-mediated energy transfer. By introducing the metal layer that generates SPPs, the system alters how optical energy is transferred to the gate, enabling efficient excitation at reduced gate dimensions.
3Reliability
If conventional photodetectors are used, then photoelectric conversion occurs, but there is a need for further increasing the internal quantum efficiency of incurring photoelectric conversion from charges directly excited by incident light
Solution Approach 1:
The patent introduces surface plasmons as an intermediary to enhance the photoelectric conversion process. The metal layer generates SPPs that increase the local electromagnetic field intensity at the gate, thereby enhancing charge excitation and improving internal quantum efficiency without fundamentally redesigning the photodetector architecture.
Solution Approach 2:
The patent enhances internal quantum efficiency by changing the energy transfer parameters through SPP generation. The metal layer modifies the local density of optical states and field distribution, increasing the probability of charge excitation per incident photon while maintaining the basic photodetector 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
This approach significantly increases the internal quantum efficiency of photoelectric conversion by leveraging the enhanced electric field effect of SPPs, allowing for efficient photocurrent generation and improved light sensing capabilities, even with smaller detector sizes.
Implementation Method 1
surface plasmons (SPs) are created by coupling between light and free electrons on a metal surface and combined with light waves into surface plasmon polaritons (SPPs)
Implementation Method 2
the SPPs create a strongly enhanced electric field at a metal-dielectric interface
Implementation Method 3
charges which have absorbed energy tunnel into the gate from a channel region formed between the oxide film and the silicon substrate or a drain electrode to which a driving voltage is applied, through the oxide film
Implementation Method 4
a photodetector may generate photocurrent by absorbing surface plasmon polaritons (SPPs), the SPPs being generated by combining surface plasmons (SPs) with photons of a light wave
Data Source
AI summary
A photodetector includes a metal layer that shields incident light and generates surface plasmon polaritons (SPPs), a light absorbing layer that absorbs the generated SPPs and allows charges excited by the absorbed SPPs and a localized electric field effect to tunnel, a dielectric formed at nanoholes in which at least a part of the metal layer is opened, and a semiconductor layer that induces the photocurrent based on an electric field effect of tunneled electrons. The SPPs form localized surface plasmons (LSPs) at an interface where the metal layer meets the dielectric.