Deep-UV LED Electrode Trench Layout for Reduced Current Crowding
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Solution Overview
Problem
Deep-ultraviolet LEDs face challenges with low light-extraction efficiency and current crowding due to high electrical resistivity in Al-containing nitride semiconductor materials, particularly in the n-type semiconductor layer, leading to inefficient charge carrier injection and operation.
Innovation Solution
A light-emitting device design featuring a semiconductor laminate with a mesa surface and trenches extending into the first semiconductor layer, where the first electrode extends into the trench, providing alternative current flow paths and reducing current crowding, thereby improving charge carrier injection efficiency and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Al-containing nitride semiconductor materials are used for the n-type semiconductor layer, then high luminous intensity and energy efficiency are achieved, but high electrical resistivity causes low charge carrier injection efficiency and current crowding
Solution Approach 1:
The n-type semiconductor layer is divided into a first semiconductor layer and a second semiconductor layer with different Al compositions. The first layer has lower Al content (20-40%) for better conductivity and charge carrier injection, while the second layer has higher Al content (40-60%) for the desired UV emission characteristics. This segmentation resolves the contradiction by separating the electrical conductivity function from the optical emission function.
Solution Approach 2:
Different regions of the semiconductor structure are assigned different Al compositions to optimize local properties. The first semiconductor layer near the electrode contact has lower Al content for low resistance and high charge carrier injection efficiency, while the active layer and second semiconductor layer have higher Al content for UV light emission. This local quality differentiation simultaneously achieves high luminous intensity and good electrical performance.
2Power
If Al-containing nitride semiconductor materials are used for the n-type semiconductor layer, then high luminous intensity is achieved, but current crowding occurs at corner portions of the electrode
Solution Approach 1:
The n-type semiconductor layer is segmented into two layers with different electrical properties. The first layer with lower Al content provides a low-resistance current distribution path that reduces current crowding at electrode corners, while the second layer maintains the high Al content needed for UV emission. This segmentation enables uniform current distribution without sacrificing luminous intensity.
Solution Approach 2:
The first semiconductor layer is optimized locally for electrical conductivity with lower Al content to prevent current crowding at electrode corners, while the second semiconductor layer is optimized for optical emission with higher Al content. This local quality optimization resolves the contradiction between achieving high luminous intensity and maintaining uniform current distribution.
3Illumination intensity
If deep-ultraviolet LEDs are designed with high Al content, then desired UV emission is achieved, but light-extraction efficiency decreases due to high electrical resistivity
Solution Approach 1:
The semiconductor structure is segmented into functional layers: the first semiconductor layer handles electrical conduction with low Al content, the active layer generates UV light with high Al content, and the second semiconductor layer provides structural support with high Al content. This segmentation ensures that high Al content is only where needed for UV emission, while electrical conduction paths maintain low resistance, thereby improving light-extraction efficiency without compromising UV emission.
Solution Approach 2:
Different Al compositions are assigned to different functional regions: lower Al content (20-40%) in the first semiconductor layer for optimal electrical conductivity and charge carrier injection, and higher Al content (40-60%) in the active layer and second semiconductor layer for UV emission. This local quality optimization simultaneously achieves desired UV emission and high light-extraction efficiency by minimizing resistive losses in current paths.
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 emission efficiency and reduces operating voltage by mitigating current crowding and improving charge carrier injection, resulting in increased brightness and stability of the light-emitting device.
Implementation Method 1
The first electrode is electrically connected to the first semiconductor layer and formed on the mesa surface, and has an extending portion that extends into the trench
Data Source
AI summary
A light-emitting device includes a semiconductor laminate, a first electrode and a second electrode. The semiconductor laminate has a mesa surface, an upper surface, a connecting surface that connects the upper surface and the mesa surface, and a lower surface opposite to the mesa surface and the upper surface. The semiconductor laminate includes a first semiconductor layer, an active layer, and a second semiconductor layer disposed in such order in a direction from the lower surface to the upper surface. The semiconductor laminate has at least one trench that extends from the mesa surface into the first semiconductor layer. The first electrode is electrically connected to the first semiconductor layer and formed on the mesa surface, and has an extending portion that extends into the trench. The second electrode is electrically connected to the second semiconductor layer and formed on the upper surface.