Light-Emitting Device Current Blockage Layer Voltage Control
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Solution Overview
Problem
The sheet resistance of the transparent electrode on the current blockage layer in light-emitting devices made of group III nitride semiconductors often increases, leading to higher drive voltage and non-uniform light emission, particularly when materials like indium oxide and oxygen-containing insulators are used.
Innovation Solution
The current blockage layer is strategically positioned and patterned such that its center is either more remote from or closer to the p-side current injection portion than the n-side current injection portion, depending on the distance between them, to control electron flow and enhance light emission uniformity, using materials like SiO2 or SiON for the blockage layer and zinc-doped indium oxide for the transparent electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a current blockage layer made of oxygen-containing insulator (SiO2 or SiON) is provided between the p-layer and transparent electrode, then light emission efficiency is improved by preventing light absorption by the p-electrode, but the sheet resistance of the transparent electrode increases, resulting in increased drive voltage
Solution Approach 1:
The patent applies local quality by making the current blockage layer non-uniform in thickness. The thickness varies from a first thickness in a first region to a second thickness in a second region. This allows different portions of the transparent electrode to have different sheet resistance characteristics, optimizing both light extraction efficiency and electrical conductivity in different areas of the device.
Solution Approach 2:
The patent changes the physical parameter of the current blockage layer by varying its thickness across different regions. This parameter change allows the structure to simultaneously achieve good light reflection properties in some regions and maintain low sheet resistance in others, resolving the contradiction between light emission efficiency and drive voltage.
2Ease of operation
If the transparent electrode is provided to cover the current blockage layer, then current diffusion to regions other than the current blockage region is enabled, but the sheet resistance of the transparent electrode on the current blockage layer increases, requiring lower sheet resistance of the transparent electrode
Solution Approach 1:
The patent applies local quality by creating regions with different current blockage layer thicknesses. The first region has a first thickness that allows good current diffusion while the second region has a second thickness that maintains lower sheet resistance, enabling both functions to coexist in different areas of the same electrode structure.
Solution Approach 2:
The patent segments the current blockage layer into different thickness regions (first region and second region), allowing each segment to perform its specialized function - one optimized for current diffusion and the other for maintaining low sheet resistance - thereby resolving the contradiction between these two requirements.
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 suppresses the increase in drive voltage and improves the uniformity of light emission by optimizing current flow and reducing the impact of higher sheet resistance, resulting in more efficient light emission across the device surface.
Implementation Method 1
cause light to be reflected at the interface between the p-layer and the current blockage layer
Implementation Method 2
a transparent electrode which is located on the p-layer and is made of a transparent, electrically conductive oxide
Implementation Method 3
a current blockage layer which is made of an insulator and is disposed between the p-layer and the transparent electrode
Data Source
AI summary
A light-emitting device has a current blockage layer formed between a p-layer and a transparent electrode. A region of the transparent electrode on the current blockage layer has a higher sheet resistance as compared with the remaining region. The current blockage layer has a circular planar pattern containing a contact portion of a p-electrode. A straight line L passing through an arbitrary position in the contact portion and extending to a contact portion of an n-electrode with the shortest distance is defined. The center O′ of the width of the current blockage layer in the direction of the straight line L is located more remote from the contact portion of the n-electrode than is the center O of the width of the contact portion of the p-electrode in the direction of the straight line L. This structure can suppress an increase in drive voltage.