ITO Reflective Layer Corrosion Prevention in Light Emitting Elements
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Solution Overview
Problem
Semiconductor light emitting elements face issues with corrosion of the ITO layer and reduced reflectance in the reflective layer, leading to decreased performance and reliability.
Innovation Solution
Incorporating a Ti-containing first layer between the ITO layer and an Al-containing second layer in the reflective layer structure, which prevents galvanic corrosion of the ITO layer while maintaining or enhancing the reflectance by optimizing the thickness of the Ti-containing layer within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective layer is stacked directly on the ITO layer, then the reflectance is increased, but the ITO layer undergoes galvanic corrosion
Solution Approach 1:
A Ti-containing first layer is introduced as an intermediary between the ITO layer and the Al-containing second layer. This intermediate layer prevents direct contact between ITO and Al, thereby preventing galvanic corrosion while maintaining the reflective function of the Al layer. The Ti layer acts as a protective barrier that mediates the interaction between the two materials.
Solution Approach 2:
The reflective layer is constructed as a composite structure with multiple layers: an ITO layer, a Ti-containing first layer, and an Al-containing second layer. This composite structure combines the transparent conducting properties of ITO with the high reflectance of Al, while the Ti layer provides corrosion protection, achieving both optical performance and material stability.
2Reliability
If the Ti-containing first layer is made thicker, then the corrosion protection is improved, but the reflectance may be affected
Solution Approach 1:
The thickness of the Ti-containing first layer is optimized within a specific range (1 nm to 10 nm) to balance two competing requirements: providing sufficient corrosion protection against the Al layer while maintaining high reflectance. By controlling the thickness parameter within this optimal range, both protection and optical performance are achieved simultaneously.
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
This configuration effectively prevents ITO layer corrosion and increases the reflectance of the reflective layer, enhancing the light emitting element's performance and reliability by ensuring stable reflectance even under high temperature conditions.
Implementation Method 1
the Ti-containing first layer is interposed between the ITO layer and the Al-containing second layer. Accordingly, a contact between the second layer and the ITO layer can be avoided, thereby preventing galvanic corrosion of the ITO layer
Implementation Method 2
the light propagating to the transparent electrode is reflected at an interface between the metal reflective layer and the insulating layer, and is extracted from the sapphire substrate via the transparent electrode
Data Source
AI summary
A light emitting element includes: a substrate; a first conductive type semiconductor layer stacked on the substrate; a light emitting layer stacked on the first conductive type semiconductor layer; a second conductive type semiconductor layer stacked on the light emitting layer; an ITO layer stacked on the second conductive type semiconductor layer; and a reflective layer stacked on the ITO layer. The substrate is transparent to an emission wavelength of the light emitting layer, and the reflective layer includes a Ti-containing first layer stacked on the ITO layer to make contact with the ITO layer and an Al-containing second layer stacked on the first layer in an opposite side to the ITO layer.