Series-Connected LED Active Layers for High Luminance
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Solution Overview
Problem
Conventional LED semiconductor elements face limitations in achieving high luminance due to current density constraints, which can lead to premature aging and reduced lifetime, and parallel connections complicate current injection with varying series resistances.
Innovation Solution
The LED semiconductor element features a series connection of two radiation-generating active layers with a contact zone that facilitates charge carrier transfer without requiring a tunnel junction, allowing for the use of materials difficult to realize epitaxially and ensuring uniform current injection through a conductive contact zone, preferably arranged in a pn-pn or np-np structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current density in the active layer is increased to generate more radiation, then the luminance is improved, but the lifetime deteriorates due to excessive ageing effects
Solution Approach 1:
The invention divides a single high-current-density active layer into multiple active layers connected in series. Each active layer operates at a lower, safe current density while the combined structure achieves high luminance through additive radiation output from multiple layers, thereby resolving the contradiction between luminance and lifetime.
2Productivity
If tunnel junctions are used to connect active layers, then charge carrier transfer is improved, but the ease of manufacture deteriorates due to difficulty in realizing tunnel junctions epitaxially
Solution Approach 1:
The invention introduces a contact zone as an intermediary structure between active layers. This contact zone provides sufficient electrical conductivity for charge carrier transfer without requiring complex tunnel junctions, thereby maintaining manufacturing simplicity while achieving the desired charge carrier transfer efficiency.
3Device complexity
If active layers are connected in parallel, then tunnel junctions become superfluous, but the ease of operation deteriorates due to difficulty in injecting the same current into both active layers with different series resistances
Solution Approach 1:
Instead of connecting active layers in parallel (which would simplify structure but complicate current control), the invention connects them in series. This inversion of the connection topology allows the same current to flow through all active layers automatically, simplifying current injection control while maintaining manageable device complexity through the use of contact zones.
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 enhances luminance by ensuring efficient charge carrier transfer and uniform current distribution, increasing the overall radiation output while maintaining a compact component size, suitable for applications like display backlighting and projection systems.
Implementation Method 1
the first active layer and the second active layer are electrically conductively connected by means of a contact zone
Implementation Method 2
A high luminance is desirable for optical applications... the amount of radiation generated depends on the current intensity with which the LED semiconductor element is operated
Data Source
AI summary
An LED semiconductor element including at least one first radiation-generating active layer and at least one second radiation-generating active layer which is stacked above the first active layer in a vertical direction and is connected in series with the first active layer, wherein the first active layer and the second active layer are electrically conductively connected by a contact zone.