Group III Nitride LED Mesa Electrode Configuration for Current Uniformity
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Solution Overview
Problem
Current group III nitride semiconductor light-emitting elements experience current concentration at the mesa end, leading to uneven light emission, local heat generation, and reduced reliability, particularly in ultraviolet light-emitting elements with an emission peak wavelength of 200 to 350 nm, which complicates manufacturing and increases operating voltage.
Innovation Solution
The solution involves modifying the n-electrode configuration by not forming or positioning the n-electrode at least 50 μm away from the mesa ends where the p-type layer is surrounded by the n-type layer, creating an n-electrode non-formation region to distribute current uniformly and reduce concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high resistance layer is formed on the p-type layer near the mesa end to suppress current concentration, then current uniformity is improved, but operating voltage increases due to increased resistance between p-electrode and semiconductor layer
Solution Approach 1:
The invention extracts the n-electrode from the mesa end region entirely, creating an n-electrode non-formation region. This removes the source of current concentration at the mesa end without introducing additional resistance layers, thereby suppressing current concentration while avoiding the operating voltage increase that would result from adding high resistance layers.
Solution Approach 2:
Instead of adding a high resistance layer to modify current distribution, the invention inverts the approach by removing the n-electrode entirely from the mesa end region. This negative formulation achieves current uniformity by eliminating the concentration mechanism rather than by adding resistance.
2Manufacturing precision
If a deep trench is formed between p-electrode and n-electrode to reduce current path variation and suppress current concentration, then current uniformity is improved, but operating voltage increases due to increased current path length and resistance
Solution Approach 1:
The invention extracts the n-electrode from the mesa end region, eliminating the need for deep trenches to control current paths. This approach suppresses current concentration by removing the electrode that causes concentration, rather than by physically separating electrodes with trenches that would lengthen current paths and increase resistance.
3Ease of manufacture
If conventional mesa structure with n-electrode at all ends is used, then manufacturing process is simple, but current concentration occurs at mesa end leading to uneven light emission and reduced reliability
Solution Approach 1:
The invention segments the n-electrode formation process by creating distinct regions: regions where the n-electrode is formed and regions where it is intentionally not formed (n-electrode non-formation regions). This segmentation allows the majority of the mesa structure to maintain simple manufacturing, while specific mesa ends are modified to prevent current concentration, thereby improving reliability without significantly complicating the overall manufacturing process.
4Illumination intensity
If n-electrode is positioned 50 μm or more away from mesa ends, then current concentration is suppressed and light emission uniformity is improved, but manufacturing precision requirement increases
Solution Approach 1:
The invention applies partial action by creating n-electrode non-formation regions only at specific mesa ends where current concentration is most problematic, rather than uniformly across all mesa ends. The 50 μm distance requirement applies only to these specific regions, allowing other areas to maintain standard electrode spacing, thereby achieving light emission uniformity without requiring excessive precision across the entire structure.
Data Source
AI summary
A group III nitride semiconductor light-emitting element is provided which includes an active layer between an n-type layer and a p-type layer, an n-electrode on the n-type layer, and a p-electrode on the p-type layer, and having a mesa structure including the p-type layer, and is characterized in that: the p-electrode has, in a top view of the group III nitride semiconductor light-emitting element, a protruding portion in a mesa end direction and an n-electrode non-formation region in the vicinity of the mesa end of a projecting end portion of the protruding portion.