GaN LED Transparent Conductive Oxide Electrode Contact Resistance
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Solution Overview
Problem
Gallium nitride based compound semiconductor light-emitting devices face challenges in achieving high light emission efficiency due to high contact resistance between the transparent conductive oxide film and the p-type semiconductor layer, which increases the driving voltage and manufacturing costs, and requires the use of contact metal layers with low light transmittance.
Innovation Solution
A method is developed to reduce contact resistance by creating a highly doped region at the interface between the p-type semiconductor layer and the transparent conductive oxide film, eliminating the need for a contact metal layer with low light transmittance, and optimizing the dopant concentration in the transparent conductive oxide film to enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact metal layer (e.g., Pt or Rh) is used to reduce contact resistance with the p-type semiconductor layer, then contact resistance is reduced, but light transmittance decreases resulting in low emission power
Solution Approach 1:
The invention extracts and removes the contact metal layer (Pt or Rh) from the electrode structure. By eliminating this layer completely, the patent avoids the trade-off between contact resistance reduction and light transmittance loss, achieving both low contact resistance and high emission power simultaneously
Solution Approach 2:
The invention changes the material parameter from metallic contact layer to transparent conductive oxide material. This parameter change enables the electrode to simultaneously achieve low contact resistance (through material selection like ITO with optimized thickness) and high light transmittance, resolving the contradiction
2Illumination intensity
If the transmittance of each layer is increased to improve light emission efficiency, then emission power increases, but contact resistance with the p-type semiconductor layer increases
Solution Approach 1:
The invention applies local quality by creating a multi-layer transparent conductive oxide structure where different layers have different thicknesses and doping concentrations. The layer in direct contact with the p-type semiconductor has optimized properties for low contact resistance, while other layers are optimized for high light transmittance, achieving both goals simultaneously
Solution Approach 2:
The invention uses composite material structure by combining multiple transparent conductive oxide layers with different compositions and properties. This composite approach allows one layer to provide low contact resistance while another layer provides high transmittance, resolving the contradiction between these two requirements
3Illumination intensity
If a rough emission surface is formed to improve light emission efficiency, then light emission efficiency improves, but the rough emission surface is damaged during formation resulting in increased contact resistance
Solution Approach 1:
The invention applies preliminary action by forming the transparent conductive oxide electrode layer before forming the rough emission surface. This sequence protects the electrode from damage during the rough surface formation process, maintaining low contact resistance while still achieving improved light emission efficiency from the rough surface
Solution Approach 2:
The transparent conductive oxide layer serves as a protective cushioning layer that is already in place before the rough surface formation process. This beforehand protection prevents direct damage to the electrode during mechanical or chemical processes used to create the rough emission surface
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 approach results in a gallium nitride based compound semiconductor light-emitting device with reduced driving voltage and improved light emission efficiency, while avoiding the use of low transmittance contact metal layers, thus lowering manufacturing costs and preventing surface damage.
Implementation Method 1
the contact resistance between the transparent conductive oxide film and the p-type semiconductor layer is reduced
Implementation Method 2
light is emitted to the outside through the positive electrode
Implementation Method 3
the light-emitting layer to have a refractive index of about 2.5 that is considerably higher than that of air
Data Source
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AI summary
The present invention provides a gallium nitride based compound semiconductor light-emitting device having high light emission efficiency and a low driving voltage Vf. The gallium nitride based compound semiconductor light-emitting device includes a p-type semiconductor layer, and a transparent conductive oxide film that includes dopants and is formed on the p-type semiconductor layer. A dopant concentration at an interface between the p-type semiconductor layer and the transparent conductive oxide film is higher than the bulk dopant concentration of the transparent conductive oxide film. Therefore, the contact resistance between the p-type semiconductor layer and the transparent conductive oxide film is reduced.