Stacked Transparent Electrodes for LED Current Spreading
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Solution Overview
Problem
Existing semiconductor light-emitting devices face challenges in evenly spreading current from the bonding pad to the p-n junction, particularly for larger chip sizes, leading to suboptimal light-emitting efficiency due to limitations in current-spreading performance with traditional GaP window layers, transparent conductive oxides, and patterned electrodes.
Innovation Solution
A semiconductor light-emitting device design featuring a substrate with a semiconductor epitaxial layer, a first transparent conductive layer, and a second transparent conductive layer, where the area of the interface between the two layers is smaller than the first layer, and the second layer has a higher conductivity and lower transmittance, alleviating current crowding and enhancing light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thicker GaP window layer is used to improve current-spreading performance, then current distribution becomes more uniform, but manufacturing time increases and throughput is reduced
Solution Approach 1:
The patent combines a thin GaP window layer with a transparent conductive oxide layer to achieve the current-spreading performance of a thick GaP layer. The composite structure allows the GaP layer to provide optical transparency while the TCO layer provides the necessary electrical conductivity for current spreading, thereby achieving good current distribution without requiring a thick GaP layer that would reduce manufacturing throughput.
Solution Approach 2:
The patent changes the electrical conductivity parameter of the window layer by introducing a transparent conductive oxide layer with high conductivity. This allows the overall window layer structure to achieve the electrical properties of a thick highly-conductive layer while maintaining a thin physical structure that enables fast manufacturing and high throughput.
2Manufacturing precision
If transparent conductive oxide layers are used to enhance current-spreading performance, then current distribution improves, but light transmittance decreases
Solution Approach 1:
The patent applies the transparent conductive oxide layer locally rather than uniformly across the entire window region. By positioning the TCO layer specifically in areas where current spreading is most needed, the structure achieves improved current distribution while minimizing the overall impact on light transmittance. The local application allows optimal balance between electrical and optical performance.
Solution Approach 2:
The patent creates a composite window layer structure combining GaP and TCO materials with complementary properties. The GaP provides high optical transmittance while the TCO provides high electrical conductivity. The composite structure allows each material to contribute its superior property, achieving both good current spreading and maintained light transmittance that neither material could achieve alone.
3Manufacturing precision
If patterned electrodes are used to improve current-spreading performance, then current distribution becomes more uniform, but light-emitting efficiency is degraded due to light absorption by opaque metal
Solution Approach 1:
The patent extracts the light-absorbing metallic component from the current-spreading electrode structure and replaces it with a transparent conductive oxide material. This extraction of the harmful opaque metal while retaining the current-spreading function through the TCO layer eliminates light absorption losses and maintains light-emitting efficiency while still achieving uniform current distribution.
Solution Approach 2:
The patent replaces the traditional opaque metal electrode with a transparent conductive oxide layer that serves as a disposable-like functional layer. The TCO layer provides the necessary electrical function without the harmful side effect of light absorption, effectively substituting a material with undesirable optical properties for one with superior optical characteristics.
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 design effectively spreads current and improves light-emitting efficiency by optimizing the arrangement and properties of the transparent conductive layers, reducing the need for additional electrode material and minimizing light absorption, thus enhancing the performance of larger light-emitting diode chips.
Implementation Method 1
a first transparent conductive layer over the outer surface; and a second transparent conductive layer over a first surface of the first transparent conductive layer
Implementation Method 2
the first transparent conductive layer has a greater transmittance to light emitted from the semiconductor epitaxial layer than that of the second transparent conductive layer
Data Source
AI summary
The luminous element includes a luminescence lamination, a second transparent oxidative conducting layer and a composite conducting layer. The composite conducting layer includes first transparent oxidative conducting layer and a metal layer. The second transparent oxidative conducting layer is positioned between the metal layer and luminescence lamination the second transparent oxidative conducting layer forms good ohmic contact with the luminous element and with metal layer. Thus, the metal layer will not be influenced by interfusion so as to maintain good light transmissivity and raise luminous efficiency of luminous element.