Nitride LED Curved Electrode Current Crowding
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Solution Overview
Problem
Nitride-based semiconductor LEDs with a planar electrode structure experience non-uniform current flow and reduced light-emission efficiency due to current crowding and light reflection issues, leading to lower luminance compared to vertical structure LEDs.
Innovation Solution
The p-type connection electrodes are formed in a line shape with an inclination angle of less than 90 degrees relative to the transparent electrode, and a line-shaped groove is introduced to expose the top surface of the n-type nitride semiconductor layer, enhancing current distribution and light-emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the p-electrode and p-type connection electrode are formed along the outermost side of the transparent electrode, then the current flow is uniformly spread in the light-emission region, but current crowding occurs in the corner where the p-electrode and p-type connection electrode are joined, reducing reliability
Solution Approach 1:
The p-type connection electrode is formed with a curved shape having a radius of curvature of 5-50 μm at the corner portion, replacing the conventional perpendicular bent shape. This curved configuration eliminates the sharp corner that causes current crowding, allowing uniform current distribution while maintaining reliability.
2Illumination intensity
If large-sized nitride based semiconductor LEDs are manufactured to uniformly spread current, then high luminance is achieved, but the effective area for light emission is reduced due to non-uniform current flow in planar structure
Solution Approach 1:
The curved p-type connection electrode eliminates current crowding at corners, enabling uniform current distribution across the entire light-emission region. This allows the effective light-emission area to be maximized while maintaining high luminance output.
3Ease of manufacture
If the n-electrode is arranged horizontally on the emission structure in planar structure, then the device can be manufactured on insulating substrates, but light reflection occurs at the n-electrode surface, reducing luminance
Solution Approach 1:
The n-electrode surface is coated with a reflective film having high reflectivity in the blue wavelength range (400-480 nm). This reflective coating redirects light that would otherwise be absorbed or reflected in harmful directions back through the light-emission region, enhancing luminance while maintaining planar structure manufacturability.
Data Source
AI summary
A nitride-based semiconductor LED comprises a substrate; an n-type nitride semiconductor layer formed on the substrate; an active layer formed on a predetermined region of the n-type nitride semiconductor layer; a p-type nitride semiconductor layer formed on the active layer; a transparent electrode formed on the p-type nitride semiconductor layer; a p-type electrode pad formed on the transparent electrode; a pair of p-type connection electrodes formed in a line extending from the p-type electrode pad so as to have an inclination angle of less than 90 degrees with respect to one side of the transparent electrode adjacent to the p-type electrode pad; a pair of p-electrodes extending from both ends of the p-type connection electrodes in the direction of the n-type electrode pad, the p-electrode being formed in parallel to one side of the adjacent transparent electrode; and an n-type electrode pad formed on the n-type nitride semiconductor layer, on which the active layer is not formed, such that the n-type electrode pad faces the p-type electrode pad.