UV Nitride LED Light Extraction via Edge Patterns
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Solution Overview
Problem
UV nitride semiconductor LEDs suffer from low light extraction efficiency due to Auger recombination and crystal defects, particularly in the short-wavelength UV region, leading to commercialization challenges.
Innovation Solution
An ultraviolet light emitting device with a substrate featuring a concave or convex edge pattern and a semiconductor laminate having uneven portions on its side surfaces, which are formed by intentional defects during growth, enhancing light extraction by scattering and directing light outward.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If UV nitride semiconductor LEDs are used for short-wavelength region (UV-B and UV-C), then high efficiency characteristics are achieved, but light extraction efficiency becomes extremely low (2% to 3%)
Solution Approach 1:
The patent introduces a reflective layer positioned at the side surface of the semiconductor light emitting device, utilizing the lateral dimension to redirect light that would otherwise be reabsorbed. This side-surface reflection mechanism adds a new dimensional approach to light extraction, converting light traveling in lateral direction into extractable light paths.
Solution Approach 2:
The reflective layer acts as an intermediary element between the semiconductor layers and the external environment. It mediates the interaction of light with the device structure by reflecting light that passes through the semiconductor layers back into the device, preventing energy loss and improving overall light extraction efficiency.
2Quantity of substance
If light travels in lateral direction in AlxGa1-xN quantum well, then more light components are generated, but light is highly likely to be reabsorbed by semiconductor layer or substrate
Solution Approach 1:
The patent extracts light that would otherwise be reabsorbed by introducing a reflective layer at the side surface. This layer captures light traveling in lateral direction and redirects it, effectively taking out the harmful reabsorption effect and converting it into useful light extraction.
Solution Approach 2:
The patent converts the harmful effect of lateral light travel (which leads to reabsorption) into a beneficial effect by using the reflective layer to redirect this light. The light that would be lost is now reflected back and can exit through other surfaces, transforming energy loss into useful light output.
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 edge pattern and uneven surfaces significantly improve light extraction efficiency by increasing the surface area for light emission, overcoming the limitations of traditional UV nitride semiconductor LEDs.
Implementation Method 1
which are formed by intentional defects during growth, enhancing light extraction by scattering and directing light outward
Data Source
AI summary
An embodiment of the present inventive concept provides an ultraviolet light emitting device comprising: a substrate having a concave or convex edge pattern disposed along an edge of an upper surface thereof; a semiconductor laminate disposed on the substrate and including first and second conductivity-type AlGaN semiconductor layers and an active layer disposed between the first and second conductivity-type AlGaN semiconductor layers and having an AlGaN semiconductor; a plurality of uneven portions extending from the edge pattern along the side surface of the semiconductor laminate in a stacking direction; and first and second electrodes connected to the first and second conductivity-type AlGaN semiconductor layers, respectively.