Plasmonic Photodetector Structure for Long-Wavelength Pixel Scaling
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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 reduced photoelectric conversion efficiency and sensitivity, especially for long wavelengths exceeding the silicon band gap energy.
Innovation Solution
A photodetector utilizing a light absorbing layer with split conduction and valence bands, generating surface plasmon polaritons (SPPs) by combining surface plasmons with photons, and inducing photocurrent through tunneling charges excited by SPPs, enhanced by a metal layer with nanoholes and a semiconductor layer, allowing for increased quantum efficiency and wavelength response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gate size is reduced to decrease detector size, then the detector size is reduced, but light excitation does not occur because the gate size is smaller than the wavelength band of incident light
Solution Approach 1:
The patent introduces surface plasmon polaritons (SPPs) as an intermediate carrier that operates at the interface between metal and dielectric, effectively adding a dimensional aspect to light-matter interaction. SPPs confine electromagnetic energy at the interface, enabling efficient coupling with sub-wavelength gate structures that would otherwise be too small to excite direct light absorption.
Solution Approach 2:
Surface plasmon polaritons serve as an intermediary between incident light and the gate structure. The metal layer converts incident photons into SPPs, which then interact with the gate to generate hot carriers that tunnel into the gate, indirectly achieving photoelectric conversion even when the gate is smaller than the incident light wavelength.
2Device complexity
If direct light absorption is used in conventional photodetectors, then the structure is simple, but the internal quantum efficiency is limited and cannot detect long wavelengths exceeding silicon band gap energy
Solution Approach 1:
The patent employs a composite structure combining metal (for SPP generation), dielectric/oxide film (for charge tunneling and field enhancement), and semiconductor (for photocurrent generation). This multi-material system enables detection of long wavelengths by converting incident photons into SPPs at the metal-dielectric interface, which then generate hot carriers that can be detected even when photon energy is below the silicon band gap.
Solution Approach 2:
The patent changes the detection mechanism from direct photon absorption to indirect detection via SPP-mediated hot carrier generation. By altering the physical parameter of light-matter interaction from direct electronic transition to plasmonic field enhancement followed by quantum tunneling, the system achieves high internal quantum efficiency for long wavelengths that would otherwise be undetectable.
3Area of moving object
If the gate size is reduced to increase pixel density, then pixel density increases, but light sensing capability decreases due to insufficient light absorption
Solution Approach 1:
The patent creates localized surface plasmon effects at the metal-dielectric interface directly above each pixel's gate region. The SPPs are confined to specific locations at the interface, generating highly localized electric field enhancement and hot carrier generation zones that are spatially correlated with the gate structure, thereby maintaining high light sensing capability even with reduced gate dimensions.
Solution Approach 2:
By utilizing the interface dimension between metal and dielectric, the patent enables light sensing in a different spatial regime than conventional bulk absorption. SPPs propagate and interact at this two-dimensional interface, allowing efficient light-matter coupling that is not constrained by the planar gate footprint, thus preserving sensing capability at high pixel densities.
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 solution enhances internal quantum efficiency, increases signal-to-noise ratio, and maximizes light sensing capability by effectively converting long-wavelength light into photocurrent, exceeding the limitations of conventional silicon photodetectors.
Implementation Method 1
utilizing the phenomenon that collective oscillations of free electrons, known as 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 photodetector is typically formed to bring about photoelectric conversion by absorbing light into the gate
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
Data Source
AI summary
A plasmonic field-enhanced photodetector is disclosed. The photodetector absorbs surface plasmon polaritons (SPPs) by using a light absorbing layer having a conduction band and a valence band in which an energy is split, the SPPs being generated by combining surface plasmons (SPs) with photons of a light wave, and generates photocurrent based on the absorbed SPPs.