Photodiode Detection Structure with Reflective Layers for Light Use Efficiency
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Solution Overview
Problem
Optical sensors face a trade-off between increasing sensor capacity and light use efficiency, as thinning the active layer of photodiodes to enhance capacity reduces the amount of light absorbable by the photodiodes, thereby decreasing light use efficiency.
Innovation Solution
A detection device design that includes a reflective layer between photodiodes, with lower electrodes having a smaller area than the gate and signal lines, and a reflective layer positioned between adjacent lower electrodes to reflect and redirect unabsorbed light back to the photodiodes, improving light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the active layer of the photodiode is thinned to increase sensor capacity, then the sensor capacity is improved, but the light use efficiency deteriorates
Solution Approach 1:
The patent converts the harmful effect of unabsorbed light (which would be lost) into a beneficial effect by introducing a reflective layer that redirects this light back to the photodiode active layer, allowing it to be absorbed and utilized for signal generation
Solution Approach 2:
The reflective layer acts as an intermediary component between the photodiode and the external environment, mediating the path of unabsorbed light to redirect it back through the active layer for additional absorption and signal generation
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 design enhances light use efficiency by reflecting unabsorbed light back to the photodiodes, thereby increasing the overall light absorption and reducing noise from external light sources, while maintaining sensor capacity.
Implementation Method 1
a reflective layer provided between the substrate and each of the photodiodes in the direction orthogonal to the substrate... the reflective layer is provided between the lower electrodes adjacent to each other in a plan view
Data Source
AI summary
A detection device includes a substrate, a plurality of photodiodes provided on the substrate, a plurality of transistors provided correspondingly to the respective photodiodes, a plurality of gate lines that extend in a first direction, a plurality of signal lines that extend in a second direction intersecting the first direction, a plurality of lower electrodes that are provided between the transistors and the photodiodes in a direction orthogonal to the substrate, and are provided correspondingly to the respective photodiodes, an upper electrode provided so as to extend across the photodiodes, and a reflective layer provided between the substrate and each of the photodiodes in the direction orthogonal to the substrate. Each of the lower electrodes has a smaller area than an area defined by the gate lines and the signal lines, and the reflective layer is provided between the lower electrodes adjacent to each other in a plan view.