Plasmonic Photodetector With Split Bands for Sub-Wavelength 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 inefficient photoelectric conversion and low internal quantum efficiency, especially for long wavelengths beyond 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, which are then absorbed and used to induce photocurrent through tunneling, enhancing light sensing capability and quantum efficiency by interacting with a metal layer and localized electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If incident light is directly absorbed into a gate of smaller size than the wavelength band, then detector size and pixel size can be reduced, but light excitation does not occur and photoelectric conversion efficiency decreases
Solution Approach 1:
The patent introduces surface plasmon polaritons (SPPs) as an intermediary mechanism to bridge the gap between incident light and the photodetector gate. SPPs are generated at a metal-dielectric interface and create a strongly enhanced electric field that enables efficient light absorption in sub-wavelength structures, thereby maintaining small detector size while achieving high photoelectric conversion efficiency
Solution Approach 2:
The patent changes the optical response parameters by utilizing plasmonic resonance effects. By adjusting the metal layer properties, dielectric constant, and SPP coupling conditions, the system achieves wavelength-selective absorption and enhanced light-matter interaction, enabling efficient detection in compact structures
2Device complexity
If conventional direct light absorption is used, then device structure is simple, but internal quantum efficiency of photoelectric conversion is low
Solution Approach 1:
The patent employs a composite structure consisting of a metal layer, dielectric layer, and semiconductor gate. This composite architecture enables plasmonic field enhancement and improved light absorption, significantly increasing internal quantum efficiency while maintaining practical device complexity through standard CMOS fabrication processes
3Measurement precision
If tunneling charges are induced by SPPs into a separate space through an insulation film, then light sensing capability is maximized and signal-to-noise ratio increases, but device structure and process complexity increases
Solution Approach 1:
The patent segments the device into distinct functional layers: a metal layer for SPP generation, a dielectric layer for field enhancement and charge tunneling, and a semiconductor gate for photocurrent induction. This segmentation enables optimized performance in each layer while maintaining overall device manageability through modular fabrication
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 significantly increases the signal-to-noise ratio and photoelectric conversion efficiency, enabling detection of long wavelengths beyond the silicon band gap energy and maximizing light sensing capability by tunneling charges excited by SPPs into a separate space, affecting the threshold voltage of the current channel.
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
Absorb Field, Transform Electromagnetic Energy to Electrical Energy
Implementation Method 3
achieve wavelength response characteristics unavailable from pure silicon by creating the effect of obtaining a plurality of split band gaps through an energy level which may be involved in coupling of SPPs
Implementation Method 4
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.