Lateral-Electrode LED Structure for Uniform Current Injection
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Solution Overview
Problem
Existing LED technologies face challenges in optimizing light emission efficiency due to the difficulty in simultaneously minimizing semiconductor stack thickness for reduced optical absorption and maximizing current uniformity across the active area, particularly with lateral electrodes, which leads to variations in charge carrier injection and performance.
Innovation Solution
Incorporating a fourth semiconductor layer that forms an energy barrier of at least 100 meV between the second and third doped layers, ensuring precise control over charge carrier injection and distribution, thereby standardizing current density and compensating for production-induced thickness non-uniformities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the semiconductor stack thickness is reduced to minimize optical absorption and maximize light extraction, then light emission efficiency is improved, but current distribution uniformity deteriorates due to variations in charge carrier injection
Solution Approach 1:
The patent introduces a fourth semiconductor layer as an intermediary between the second and third doped layers. This intermediate layer forms an energy barrier that mediates the charge carrier transport, ensuring uniform current distribution across the active area while maintaining the reduced stack thickness for optimal light extraction.
Solution Approach 2:
The patent modifies the energy barrier parameter by introducing the fourth layer with specific bandgap characteristics. This parameter change creates an energy barrier of at least 100 meV that controls charge carrier injection, enabling uniform current distribution in thin-stack LEDs where conventional structures fail to achieve uniformity.
2Loss of energy
If a lateral electrode is used to free the emissive surface, then light extraction efficiency is improved, but charge carrier injection uniformity deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform energy barrier distribution through the fourth layer. The energy barrier is strategically positioned to compensate for the non-uniform injection characteristics of the lateral electrode, ensuring uniform current distribution across different regions of the active area.
3Productivity
If the semiconductor stack is made thinner to improve light extraction, then extraction efficiency is improved, but performance consistency deteriorates due to production-induced thickness non-uniformities
Solution Approach 1:
The fourth layer acts as a cushioning layer that compensates for thickness variations before they affect the active area performance. By positioning this layer with appropriate energy barrier characteristics, the patent pre-compensates for production-induced non-uniformities, ensuring consistent LED performance across batches.
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 enhances light-emitting diode efficiency by ensuring uniform current distribution and precise charge carrier injection, improving the electro-optical performance and consistency across LEDs, especially in thin LEDs with small lateral dimensions.
Implementation Method 1
the semiconductor of the fourth layer forms, with respect to the semiconductor of the third layer, an energy barrier of at least 100 meV opposing a circulation of electric charge carriers according to the second type of conductivity from the second electrode to the second layer
Data Source
Figure 1~2c
Figure 3A~3C
Figure 3D~3F
AI summary
Light-emitting diode (100) comprising: - a first electrode (102); - a first semiconductor layer (104) doped according to a first type of conductivity; - a second semiconductor layer (108) doped according to a second type of conductivity; - a radiative recombination region (114) disposed between, or at the interface of, the first and second layers; - a third semiconductor layer (118) doped according to the second type of conductivity; - a fourth semiconductor layer (120) disposed between the second and third layers; - a second electrode (124) disposed against a lateral face (126) of the third layer and against only a part of a lateral face (128) of the fourth layer; and wherein the fourth layer (120) forms, with respect to the third layer, an energy barrier of at least 100 meV.