Micro LED Transition Structure for Higher Internal Quantum Efficiency
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Solution Overview
Problem
Maintaining high internal quantum efficiency (IQE) in micro light-emitting devices (LEDs) is a challenge due to issues like non-radiative recombination on sidewalls and increased thermal effects in conventional micro LEDs, which affect luminous efficiency.
Innovation Solution
The micro LED design includes a transition structure with sequentially disposed first, second, and third transition units, an active structure with quantum well structures, and a hole injection layer, optimized in composition and thickness to control electron flow and reduce lattice mismatch, thereby enhancing IQE. The structure features specific compositions for barrier and well layers and a hole injection layer with reduced Al concentration to prevent hole movement to sidewalls, ensuring efficient recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional micro LED structure is used, then device size is reduced and integration is improved, but internal quantum efficiency deteriorates due to non-radiative recombination on sidewalls
Solution Approach 1:
An electron blocking layer with specific Al concentration (not greater than the barrier layer of quantum well structures) is introduced as an intermediary between the active structure and p-type semiconductor layer. This layer mediates the interaction between electrons and the p-type layer, blocking non-radiative recombination at the interface while allowing radiative recombination in the quantum well structures, thus improving IQE in miniaturized devices
Solution Approach 2:
The patent applies local quality by creating spatial variation in Al concentration across different layers. The electron blocking layer has lower Al concentration than the quantum well barrier layers, creating a localized property distribution that optimizes electron blocking at the interface while maintaining quantum confinement in the active region, addressing sidewall recombination issues in small devices
2Productivity
If Al concentration in hole injection layer is increased to improve hole injection, then hole injection efficiency is improved, but hole movement to sidewalls increases causing non-radiative recombination
Solution Approach 1:
The patent changes the Al concentration parameter in the hole injection layer to be not greater than that of the quantum well barrier layers. This parameter optimization ensures sufficient hole injection into the active structure while preventing excessive hole diffusion to sidewalls, thereby reducing non-radiative recombination losses in miniaturized LED structures
3Reliability
If quantum well structure barrier layer Al concentration is increased to improve electron blocking, then electron confinement is improved, but hole injection becomes more difficult
Solution Approach 1:
The patent segments the electron blocking function into two distinct layers: the quantum well barrier layers with high Al concentration for electron confinement, and a separate electron blocking layer with lower Al concentration for hole injection facilitation. This segmentation allows each layer to optimize its specific function without compromising the other, improving both electron confinement and hole injection efficiency
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 design improves the internal quantum efficiency of micro LEDs by optimizing electron and hole injection, reducing non-radiative recombination, and enhancing luminous efficiency by ensuring effective utilization of electric currents and reducing thermal effects.
Implementation Method 1
The active structure is disposed between the transition structure and the p-type semiconductor layer, and includes an M number of quantum well structures
Implementation Method 2
the barrier layer has an Al concentration that is 1.2 to 3 times an Al concentration of the barrier layer of each of the M number of quantum well structures
Implementation Method 3
The hole injection layer has an Al concentration that is not greater than the Al concentration of the barrier layer of each of the M number of quantum well structures
Data Source
AI summary
A micro LED includes an n-type semiconductor layer, a p-type semiconductor layer, a transition structure, an active structure and a hole injection layer. The transition structure includes first to third transition units. The active structure includes an M number of quantum well structures. Each of the M number of quantum well structures includes a barrier layer and a well layer. The third transition unit includes a Q number of layer units each including a barrier layer and a well layer. In each of the Q number of layer units, the barrier layer has an Al concentration that is 1.2 to 3 times an Al concentration of the barrier layer of each 10 of the M number of quantum well structures. The hole injection layer has an Al concentration that is not greater than the Al concentration of the barrier layer of each of the M number of quantum well structures.