LED Transparent Current Spreading Layer for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diode (LED) devices with textured surfaces enhance light extraction efficiency but compromise lateral current conduction and spreading, resulting in higher forward voltage and potential peeling issues.
Innovation Solution
A light-emitting device with a semiconductor contact layer having a rough top surface and a transparent current spreading layer, where the rough surface is directly under the current spreading layer, and the angles between oblique lines formed by connecting crests and troughs on both surfaces differ by no more than 10 degrees, or are substantially the same, to improve current conduction and adhesion while maintaining light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the semiconductor layer has a textured surface, then light extraction efficiency is improved, but lateral current conduction and current spreading are lowered
Solution Approach 1:
A transparent current spreading layer is introduced as an intermediary between the textured semiconductor contact layer and the upper electrode. This layer mediates between the light extraction function of the textured surface and the current conduction requirement, providing a path for lateral current spreading while allowing light to pass through to the phosphor layer.
Solution Approach 2:
The device uses a composite structure combining a textured semiconductor contact layer with a transparent current spreading layer. The semiconductor layer provides light extraction through its textured surface, while the transparent current spreading layer provides lateral current conduction, creating a system where each layer performs its specialized function without compromising the other.
2Loss of energy
If the semiconductor layer has a textured surface, then light extraction efficiency is improved, but forward voltage is higher
Solution Approach 1:
The transparent current spreading layer acts as a mediator that reduces the forward voltage by providing improved lateral current conduction paths. This allows current to spread more effectively across the textured semiconductor surface, reducing concentration effects and lowering the overall forward voltage while preserving the light extraction benefits of the textured surface.
3Loss of energy
If the semiconductor layer has a textured surface, then light extraction efficiency is improved, but adhesion strength is reduced causing peeling issues
Solution Approach 1:
The transparent current spreading layer forms a composite structure that bridges the textured semiconductor contact layer and the upper electrode. This composite approach allows the textured semiconductor layer to maintain its light extraction function while the additional transparent layer provides enhanced adhesion and mechanical stability, preventing peeling issues.
Solution Approach 2:
The textured surface is maintained in the semiconductor contact layer for light extraction, while the transparent current spreading layer provides a smoother, more adherent surface for the upper electrode. Each layer has optimized local properties: the semiconductor layer has high texture for light extraction, while the transparent layer has good adhesion properties.
Data Source
AI summary
A light-emitting device comprising: a light-emitting stacked layer having a first conductivity type semiconductor layer; a light-emitting layer formed on the first conductivity type semiconductor layer; and a second conductivity type semiconductor layer formed on the light-emitting layer; a transparent conductive oxide layer formed on the second conductivity type semiconductor layer wherein the transparent conductive oxide layer having a first portion and a second portion and the upper surface of the transparent conductive oxide layer is a textured surface; a first electrode formed on the second portion of the transparent conductive oxide layer, and a second electrode formed on the first conductivity type semiconductor layer; a planarization layer formed on the first portion of the transparent conductive oxide layer, and the second electrode; and a reflective layer formed on the planarization layer that is devoid of the first electrode and the second electrode.