GaN LED Super Lattice V Pits Hole Injection
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Solution Overview
Problem
The low hole concentration and mobility in P-GaN material limit the injection depth in multi-quantum well (MQW) of GaN-based LEDs, restricting the improvement of light-emitting efficiency.
Innovation Solution
Incorporating a granular medium layer to form V pits of different widths and depths in the super lattice, which enhances hole injection efficiency and uniformity across all quantum wells, thereby improving the lighting efficiency of LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional super lattice growth is used at low temperature, then V pits are formed due to threading dislocation, but the initial formation positions and sizes are basically consistent, resulting in high hole injection efficiency in specific multi-quantum well position yet low injection efficiency in other quantum wells
Solution Approach 1:
The patent introduces granular medium layers with different grain sizes (0.5-5 nm) at different depths within the super lattice structure. These granular layers create V pits with varying widths and depths at different locations, making each region have tailored hole injection characteristics. This local variation in V pits geometry optimizes hole injection efficiency across all quantum wells rather than uniform formation
Solution Approach 2:
The patent modifies the physical and chemical parameters of the super lattice by inserting granular medium layers composed of specific materials (Mg, Si, Ti, Zr, Hf, Ta oxides or nitrides). These granular layers change the local crystal structure, dislocation density, and epitaxial growth conditions, resulting in V pits with controlled different widths (50-500 nm) and depths, thereby optimizing hole injection across multiple quantum wells
2Reliability
If P-GaN material is used with low hole concentration and mobility, then the injection depth in multi-quantum well is limited, but this restricts further improvement of GaN-based LED light-emitting efficiency
Solution Approach 1:
The patent introduces granular medium layers as intermediary structures within the super lattice that facilitate hole injection. These granular layers act as mediators that create V pits serving as preferential pathways for hole injection into the multi-quantum well structure, overcoming the limited hole injection capability of P-GaN material with low concentration and mobility
Solution Approach 2:
The granular medium layers create a porous-like structure with V pits of different sizes and depths within the super lattice. This porous architecture increases the surface area and creates multiple injection channels for holes, thereby improving overall hole injection efficiency and enabling better utilization of the multi-quantum well structure for enhanced light-emitting 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
The adjusted V pits distribution significantly improves hole injection efficiency and uniformity, leading to enhanced light-emitting efficiency in LEDs by optimizing the space distribution of holes in MQW.
Implementation Method 1
the super lattice growth layer is of low temperature, and the nitride (such as GaN) has poor lateral epitaxy. This time, V pits would be formed due to threading dislocation
Data Source
AI summary
A light-emitting diode includes from bottom to up: a substrate, a first-conductive type semiconductor layer, a super lattice, a multi-quantum well layer and a second-conductive type semiconductor layer. At least one layer of granular medium layer is inserted in the super lattice. The granular medium layer is used for forming V pits with different widths and depths in the super lattice. The multi-quantum well layer fills up the V pits and is over the top surface of the super lattice. The number of micro-particle generations, positions and densities can be adjusted by introducing granular medium layers and controlling the number of layers, position and growth conditions during super lattice growth process, to ensure V pits of different depths and densities. This can change hole injection effect, effectively improve hole injection efficiency and distribution uniformity in all quantum wells, thus improving LED light-emitting efficiency.