Hot-Electron Infrared Detector Using Light Trapping in Silicon
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Solution Overview
Problem
Conventional photonic infrared detectors using low band gap materials like InGaAs, InSb, or HgCdTe are expensive, rare, or toxic, and require precise fabrication techniques for efficient IR detection, limiting their scalability and cost-effectiveness.
Innovation Solution
A photonic infrared detector design utilizing a 10-30 nm thick metal metasurface with broad-band IR absorption, where light takes multiple passes within a crystalline Si substrate, and a dielectric SiO2 layer to reduce charge carrier recombination and absorption on the bottom side, allowing for scalable and cost-effective fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional low band gap materials (InGaAs, InSb, HgCdTe) are used for IR detection, then detection performance is achieved, but cost, availability, and safety deteriorate due to rarity, expense, and toxicity
Solution Approach 1:
The invention changes the material parameter from conventional low band gap materials to crystalline Si with a different band gap, combined with hot electron injection mechanism, achieving IR detection at room temperature while using abundant, cheap, and non-toxic silicon
Solution Approach 2:
The invention replaces expensive, rare materials with cheap crystalline Si, making the detector economically viable for mass production while maintaining detection functionality through the hot electron mechanism
2Productivity
If metal layer thickness is reduced to electron mean free path (few tens of nm) for efficient electron transport, then electron transport efficiency improves, but optical absorption capability deteriorates
Solution Approach 1:
The invention adds a temporal dimension by allowing light to make multiple passes through the thin metal layer, compensating for the reduced absorption in the thin layer through repeated interaction opportunities
Solution Approach 2:
The light trapping structure enables continuous absorption of photons across multiple passes, maintaining effective absorption despite the thin metal layer thickness, while hot electrons are continuously injected into Si
3Loss of energy
If small-scale metamaterials or deep trench resonators are used for strong SPP absorption, then resonant absorption improves, but fabrication complexity and precision requirements worsen
Solution Approach 1:
The invention extracts the essential function of SPP excitation from complex metamaterial structures and implements it through a simpler planar metal layer combined with light trapping, removing the need for expensive electron beam lithography
Solution Approach 2:
Instead of using complex topological structures to achieve absorption, the invention inverts the approach by using a simple planar structure with light trapping from the substrate side, achieving strong absorption without complex fabrication
4Loss of energy
If light is strongly absorbed in a single pass through thin metal layer, then absorption efficiency improves, but the metal layer thickness must increase, worsening electron transport before thermalization
Solution Approach 1:
The invention adds a spatial dimension by introducing light trapping structures in the substrate that cause light to propagate multiple times through the thin metal layer, achieving high absorption without increasing thickness
Solution Approach 2:
The invention creates a composite structure combining thin metal layer with light trapping substrate structures, achieving synergistic effect where the substrate structures enable multiple light passes through the thin metal, solving both absorption and thickness constraints
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
Achieves over 85% broad-band IR absorption with reduced fabrication complexity and cost, enabling efficient IR detection using abundant and cheaper crystalline Si, while minimizing charge carrier recombination and reflection.
Implementation Method 1
Surface plasmon polaritons (SPPs) can be excited at the metal surface
Implementation Method 2
The photoexcited electrons in the metal can then be injected into the conduction band of c-Si before being thermalized, and electric current can be generated. These non-thermalized electrons, called hot electrons, enable the detection of IR light with energies below the c-Si band gap.
Implementation Method 3
the dielectric layer also electronically passivates the Si surface to reduce the charge carrier recombination
Implementation Method 4
the top surface of the Si wafer is structured in such a way that admits the incident light into the substrate and prevents the light from leaking out of the substrate
Implementation Method 5
an antireflection coating (ARC) that is applied to the metal structures to reduce reflection at the top surface
Data Source
AI summary
A photonic infrared detector having at least one metal layer having a broad-band IR absorption and the detector is configured to enable light to make a plurality of passes within a c-Si substrate.