Biased Dielectric-Metal Filter for UV Photodetector Quantum Efficiency
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Solution Overview
Problem
Photodetectors, particularly those sensitive to ultraviolet wavelengths, face challenges in maximizing quantum efficiency due to light absorption close to the silicon surface and instability in humid environments or high UV radiation, with existing solutions like back illumination and anti-reflection coatings being inadequate for all wavelengths and prone to degradation.
Innovation Solution
A photodetector design incorporating a metal-dielectric filter acting as a band-pass filter combined with a bias voltage applied between the substrate and metal layer to enhance signal charge collection, providing improved quantum efficiency and wavelength selection, using a dielectric-metal-dielectric arrangement to form an induced transmission filter (ITF) for efficient ultraviolet radiation handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back illumination arrangement is used to improve quantum efficiency at ultraviolet wavelengths, then light transmission into the detector is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies back illumination by inverting the conventional illumination direction, allowing ultraviolet light to enter through the back surface of the silicon substrate. This inversion improves quantum efficiency at UV wavelengths by avoiding front surface reflections and absorption, while the substrate itself serves as the optical path without requiring additional complex optical components.
Solution Approach 2:
The patent modifies the operational parameters by applying a biased voltage to the metal layer in the dielectric-metal-dielectric filter structure. This parameter change enhances the electric field distribution to improve charge collection efficiency specifically for ultraviolet wavelengths, thereby improving quantum efficiency without adding mechanical complexity.
2Reliability
If anti-reflection coatings are applied to maximize light transmission, then quantum efficiency is improved, but the device complexity and manufacturing steps increase
Solution Approach 1:
The metal layer in the dielectric-metal-dielectric filter structure serves multiple functions: it acts as both a filtering element for wavelength selection and as an electrode for applying bias voltage to enhance charge collection. This multi-functionality eliminates the need for separate anti-reflection coatings and biasing electrodes, reducing overall device complexity while maintaining improved quantum efficiency.
3Reliability
If traditional passivation methods are used to improve charge collection efficiency, then quantum efficiency is improved, but stability in humid environments and high UV radiation deteriorates due to degradation
Solution Approach 1:
The patent employs a composite dielectric-metal-dielectric filter structure where the dielectric layers provide protective and insulating properties while the metal layer provides conductivity and biasing capability. This composite structure offers enhanced stability in humid environments and under high UV radiation compared to traditional single-material passivation layers, as the dielectric materials can be selected for their environmental resistance properties.
4Measurement precision
If a band pass filter is added to provide wavelength selection, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the band pass filter function with the biasing electrode function by integrating the dielectric-metal-dielectric filter structure directly into the detector architecture. The metal layer serves dual purposes as both the filtering element and the biasing electrode, eliminating the need for separate filter components and reducing overall device complexity while maintaining precise wavelength selection capability.
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 quantum efficiency while providing selective wavelength sensitivity, offering improved stability and passivation without the degradation issues of traditional methods, particularly beneficial in the ultraviolet range.
Implementation Method 1
A photodetector includes a metal-dielectric filter acting as a band pass filter on the radiation receiving surface of the detector
Implementation Method 2
using a dielectric-metal-dielectric arrangement to form an induced transmission filter (ITF) for efficient ultraviolet radiation handling
Implementation Method 3
combined with a connector to apply bias voltage between the substrate of the detector and the metal layer of the filter to increase efficiency of signal charge collection
Implementation Method 4
incident radiation is converted at the image area into signal charge which is representative of the intensity of the radiation impinging on the array of pixels
Data Source
AI summary
A photodetector comprises a semiconductor substrate having an input surface for receiving illumination, control electrodes for control of photogenerated charge within the substrate and a filter on the radiation input surface of the substrate, the filter comprising a dielectric-metal band pass filter having a metal layer and one or more dielectric layers with one dielectric layer between the substrate surface and the metal layer. A connector is provided for applying a bias voltage to the metal layer with respect to the substrate. In effect, the metal layer of the band pass filter provides two functions. The first function is as part of the ITF filter selecting the wavelength desired for the device. The second function is as a conductive layer allowing a bias to be provided between the substrate and the metal layer thereby producing a field within the surface of the substrate to which the filter is applied.