Nitride Semiconductor Pad Electrode Adhesion and Light Extraction
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Solution Overview
Problem
Nitride semiconductor light emitting devices face issues with adhesion strength between conductive oxide films and pad electrodes, leading to inadequate current supply and light extraction efficiency.
Innovation Solution
A nitride semiconductor device structure incorporating a conductive oxide film and a pad electrode with a junction layer containing a first metal, such as Titanium, and a pad layer with a second metal of higher reflectivity, like Rhodium, to enhance adhesion and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer pad electrode is used on the conductive oxide film, then the structure is simple, but the adhesion strength is insufficient
Solution Approach 1:
The pad electrode is divided into multiple layers: a first pad electrode layer (Ti) for adhesion to the conductive oxide film, and a second pad electrode layer (Al) for electrical connection and reflectivity. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between structural simplicity and adhesion strength.
Solution Approach 2:
The pad electrode uses a composite structure combining different materials (Ti and Al) with complementary properties. Ti provides strong adhesion to ITO, while Al provides high reflectivity and electrical conductivity. This composite approach solves the adhesion problem without requiring complex multi-component systems.
2Reliability
If Rh, Pt, or W is used as the pad electrode material for good adhesion, then adhesion strength improves, but current flow between the conductive oxide film and pad electrode becomes insufficient
Solution Approach 1:
Different regions of the pad electrode structure have different material compositions optimized for their specific functions. The first layer (Ti) has high adhesion quality for bonding to ITO, while the second layer (Al) has high electrical conductivity quality for current flow. This local optimization resolves the contradiction between adhesion and current flow.
Solution Approach 2:
The first pad electrode layer (Ti) acts as an intermediary between the conductive oxide film (ITO) and the second pad electrode layer (Al). It facilitates both mechanical adhesion and electrical current flow, mediating the interaction between the ITO and Al layers and solving the problem of insufficient current flow when using highly adhesive materials like Rh or Pt.
3Reliability
If the pad electrode material is selected only for adhesion to conductive oxide film, then adhesion improves, but light extraction efficiency decreases
Solution Approach 1:
The pad electrode is segmented into two layers with distinct functions: the first layer (Ti) handles adhesion to the conductive oxide film, while the second layer (Al) handles light extraction with its high reflectivity. This functional segmentation resolves the contradiction between adhesion and light extraction efficiency.
Solution Approach 2:
The second pad electrode layer (Al) is positioned specifically to provide high reflectivity for light extraction, while the first layer (Ti) provides adhesion. This local quality optimization ensures that adhesion requirements are met without compromising light extraction performance.
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
Improves adhesion between the conductive oxide film and the pad electrode, ensuring uniform current injection and enhanced light extracting efficiency in nitride semiconductor light emitting devices.
Implementation Method 1
adhesion between the pad electrode and the conductive oxide film can be improved
Implementation Method 2
a pad layer including a second metal that is different from the first metal... enhanced light extracting efficiency
Data Source
AI summary
A nitride semiconductor device includes a conductive oxide film with high reliability is provided. The nitride semiconductor device having a nitride semiconductor layer includes a conductive oxide film on the nitride semiconductor layer and a pad electrode on the conductive oxide film. The pad electrode includes a junction layer that contains a first metal and is in contact with the conductive oxide film, and a pad layer that contains a second metal.