Semiconductor Light Emitting Device Electrode Segmentation
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Solution Overview
Problem
High current injection density issues in light emitting diodes (LEDs) with reflective metal layers lead to reduced light emission efficiency due to lateral spreading of current, making it difficult to achieve higher optical output.
Innovation Solution
A semiconductor light emitting device structure is designed with a first contact layer between the window layer and the electrode, and a second contact layer on the current spreading layer, where the first contact layer has a higher conductivity than the window layer and is selectively positioned to reduce contact resistance and prevent lateral current spread, enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective metal layer is used to improve light extraction efficiency, then light emission intensity increases, but current spreads laterally causing reduced current injection density
Solution Approach 1:
The reflective metal layer is segmented into a reflection electrode and a non-reflection electrode region. The reflection electrode is positioned to reflect light while the non-reflection electrode region allows concentrated current injection into the light emitting layer, preventing lateral current spread while maintaining light extraction efficiency.
Solution Approach 2:
Different regions of the electrode structure are assigned different optical properties: the reflection electrode has high reflectivity for light extraction, while the non-reflection electrode region has low reflectivity to concentrate current injection. This local differentiation resolves the contradiction between light extraction and current concentration.
2Productivity
If current injection density is increased to improve light emission efficiency, then optical output increases, but lateral current spread reduces effective current injection density
Solution Approach 1:
The electrode is segmented into regions with different current injection characteristics. The non-reflection electrode region concentrates current vertically into the light emitting layer, while the reflection electrode region handles light reflection, separating current injection function from light extraction function.
Solution Approach 2:
The non-reflection electrode region acts as an intermediary that facilitates concentrated current injection into the light emitting layer without causing lateral spread, enabling high effective current injection density while maintaining overall device performance.
3Device complexity
If electrode structure is simplified to reduce manufacturing complexity, then device complexity decreases, but light extraction efficiency and current injection control deteriorate
Solution Approach 1:
The electrode is divided into reflection electrode and non-reflection electrode regions, creating a segmented structure that simultaneously achieves light extraction and current concentration functions without requiring complex multi-layer designs.
Solution Approach 2:
The segmented electrode structure performs multiple functions: the reflection electrode extracts light while the non-reflection electrode region concentrates current, allowing a single electrode structure to handle both light extraction and current injection control.
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 increases light emission intensity by 20% or more while maintaining low forward voltage and improving reliability, by ensuring effective current injection density and light extraction without lateral spreading of the light emitting region.
Implementation Method 1
The first contact layer has a higher conductivity than the window layer
Implementation Method 2
light emitted downward from a light emitting layer is reflected upward by the reflective metal layer
Implementation Method 3
a light emitting layer is provided on the first conductivity type layer
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes a substrate, a first electrode, a first conductivity type layer, a light emitting layer, a second conductivity type layer and a second electrode. The first conductivity type layer includes a first contact layer, a window layer having a lower impurity concentration than the first contact layer and a first cladding layer. The second conductivity type layer includes a second cladding layer, a current spreading layer and a second contact layer. The second electrode includes a narrow-line region on the second contact layer and a pad region electrically connected to the narrow-line region. Band gap energies of the first contact and window layers are larger than that of the light emitting layer. The first contact layer is provided selectively between the window layer and the first electrode and without overlapping the second contact layer as viewed from above.