Group III Nitride Electrode Silver Migration Prevention
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Solution Overview
Problem
In Group III nitride-based compound semiconductor light-emitting devices, silver ion migration occurs during electrical passage and thermal treatment, leading to inter-diffusion with gold, which affects device performance and light extraction efficiency.
Innovation Solution
A positive electrode structure is developed, comprising a light-transmitting electrode layer, a silver or silver alloy reflecting electrode layer, and a conductive diffusion-preventing layer, which are sequentially stacked on the p-type semiconductor layer, preventing silver migration and inter-diffusion with gold. This structure includes a light-transmitting electrode layer such as ITO, a silver alloy reflecting electrode layer with additives like copper and oxygen, and a diffusion-preventing layer made of high-melting-point metals or metal nitrides like platinum and titanium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver-containing reflecting electrode layer is formed directly on the p-type Group III nitride-based compound semiconductor layer, then light extraction efficiency is improved, but silver ion migration occurs during electrical passage and thermal treatment
Solution Approach 1:
A light-transmitting electrode layer is introduced as an intermediary between the p-type Group III nitride-based compound semiconductor layer and the silver-containing reflecting electrode layer. This intermediate layer prevents direct contact between silver and the semiconductor, thereby blocking silver ion migration during electrical passage and thermal treatment while still allowing light to pass through for efficient light extraction.
Solution Approach 2:
The electrode structure is segmented into multiple distinct layers: a light-transmitting electrode layer, a silver-containing reflecting electrode layer, and optionally a diffusion-preventing layer. This segmentation separates the functions of electrical contact, light reflection, and migration prevention into different layers, allowing each layer to optimize its specific function without compromising the others.
2Power
If the silver electrode layer is thermally treated to enhance Ohmic contact with the semiconductor layer, then electrical conductivity is improved, but silver ion migration is promoted
Solution Approach 1:
The light-transmitting electrode layer serves as a protective intermediary that allows thermal treatment to enhance Ohmic contact between the silver layer and the semiconductor without enabling silver ion migration. The intermediary layer blocks the migration path while permitting the thermal treatment to proceed for improving electrical conductivity.
Solution Approach 2:
The light-transmitting electrode layer is formed preliminarily before the silver-containing reflecting electrode layer. This preliminary structure prevents silver ion migration during subsequent thermal treatment processes that are intended to enhance Ohmic contact, thereby allowing the thermal treatment to proceed without the harmful side effect of silver migration.
3Ease of manufacture
If silver comes into direct contact with the gold pad electrode, then inter-diffusion between silver and gold occurs during passage of electricity or heating
Solution Approach 1:
The light-transmitting electrode layer acts as an intermediary barrier between the silver-containing reflecting electrode layer and the gold pad electrode. This intermediate layer prevents direct contact between silver and gold, thereby blocking inter-diffusion during electrical passage or heating while maintaining a relatively simple manufacturing process.
Solution Approach 2:
The electrode structure is segmented to include a diffusion-preventing layer between the silver-containing reflecting electrode layer and the gold pad electrode. This segmentation creates a physical barrier that prevents inter-diffusion between silver and gold, maintaining material purity and reliability while adding only a thin intermediate layer that does not significantly complicate manufacturing.
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 solution effectively prevents silver migration and inter-diffusion, ensuring stable Ohmic contact and enhanced light extraction efficiency without the need for additional thermal treatment, thereby improving the performance and reliability of the light-emitting device.
Implementation Method 1
a light-transmitting electrode layer... formed on the p-type AlxGayIn1-x-yN layer 13
Implementation Method 2
a reflecting electrode layer formed from silver or a silver-base alloy... formed on the light-transmitting electrode layer
Implementation Method 3
a conductive diffusion-preventing layer for preventing migration of silver to an upper layer with respect thereto
Implementation Method 4
ensuring stable Ohmic contact... improving the performance and reliability of the light-emitting device
Data Source
AI summary
An object of the invention is to prevent migration of silver contained in an electrode of a Group III nitride-based compound semiconductor light-emitting device. A positive electrode is formed on a p-type layer. In the positive electrode, an ITO light-transmitting electrode layer, a silver alloy reflecting electrode layer, a diffusion-preventing layer in which a Ti layer and a Pt layer are stacked, and a gold thick-film electrode are sequentially stacked on the p-type layer. The reflecting electrode layer made of a silver alloy contains palladium (Pd) and copper (Cu) as additives and also contains oxygen (O). By virtue of this structure, migration of silver from the silver alloy reflecting electrode layer and blackening of the interface between the silver alloy layer and the ITO light-transmitting electrode layer disposed thereunder are prevented, whereby light extraction efficiency can be enhanced.