Photodetector Diffracting Stack Quantum Efficiency
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Solution Overview
Problem
Semiconductor photodetectors, particularly those of small dimensions or with thin semiconductor layers, face low quantum efficiency in converting photons into electron-hole pairs, leading to inefficient light detection, especially for low-intensity light.
Innovation Solution
A photodetector design featuring a stack of diffracting elements with pads and regions of specific optical indices, where the pads are smaller than the operating wavelength, and an intermediate transparent layer enhances photon absorption by creating a complementary diffraction effect, increasing the quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lateral dimensions of the photodetector are reduced to be small, then the device size is decreased, but the quantum efficiency of photon conversion deteriorates
Solution Approach 1:
The patent introduces a vertical stack of diffracting elements above the photodetector surface, transitioning from a planar 2D structure to a 3D vertical structure. This allows light to be diffracted and guided into the active layer from multiple angles and depths, significantly improving photon absorption in small-sized devices without increasing lateral dimensions.
Solution Approach 2:
The patent introduces an intermediate transparent layer with high refractive index between the diffracting elements and the photodetector. This intermediary layer enhances light coupling and guides photons more effectively into the active layer, resolving the contradiction between small device size and low quantum efficiency by providing an optical mediation mechanism.
2Manufacturing precision
If the semiconductor layer thickness is reduced, then the manufacturing precision is improved, but the photon absorption efficiency deteriorates
Solution Approach 1:
By stacking diffracting elements vertically above the thin semiconductor layer, the patent compensates for the reduced absorption path length within the layer. The diffracting elements create multiple light paths and increase the effective interaction length between light and the semiconductor material in the vertical dimension, maintaining high conversion rates despite thin layer thickness.
Solution Approach 2:
The patent segments the light interaction process into multiple stages: diffracting elements at different vertical positions sequentially guide and focus light into the thin semiconductor layer. This segmentation allows the thin layer to be efficiently illuminated from multiple angles and positions, compensating for its limited thickness.
3Device complexity
If a single pad diffracting element is used, then the device complexity is reduced, but the quantum efficiency improvement is insufficient
Solution Approach 1:
The patent utilizes the vertical dimension by stacking multiple diffracting elements at different heights above the photodetector surface. This vertical arrangement creates a three-dimensional light guiding structure that progressively focuses and directs light into the active layer, achieving high quantum efficiency without significantly increasing lateral device complexity.
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 described design significantly increases the quantum efficiency of photon conversion, achieving a notable gain in absorption rates, even in small-sized photodetectors, by optimizing the arrangement and materials of diffracting elements and an intermediate layer.
Implementation Method 1
a stack of first and second diffracting elements, the second element being above the first element... the first element comprises at least one pad made of a material of optical index n1 laterally surrounded by a region made of a material of optical index n2 different from n1; the second element comprises at least one stud made of a material of optical index n3 laterally surrounded by a region made of a material of optical index n4 different from n3
Implementation Method 2
the intermediate layer has a thickness of between 40 and 150 nm and has an optical index greater than 2.5
Implementation Method 3
a photodetector comprising a photoelectric conversion structure made of a semiconductor material... converting photons into electron-hole pairs
Data Source
AI summary
The invention relates to a photodetector comprising a photoelectric conversion structure in a semiconductor material, and, on a photoreceptive surface of the conversion structure, a stack of first (21) and second (23) diffracting elements, the second element being above the first element, in which: the first element (21) has at least one pad (21a) in a material of optical index n1 surrounded laterally by a region (21b) in a material of optical index n2 different from n1; the second element (23) has at least one pad (23a) in a material of optical index n3 surrounded laterally by a region (23b) in a material of optical index n4 different from n3; the pads (21a, 23a) of the first and second elements are substantially vertically aligned; and the differences in optical indices n1-n2 and n3-n4 are of opposite signs.