Micro LED Mesa Structure With Schottky Edge Depletion
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Solution Overview
Problem
Micro LEDs suffer from low efficiency due to non-radiative recombination at the mesa edges, which is exacerbated by the small size of the mesas and the etching process used in their formation.
Innovation Solution
The micro LED element is designed with a mesa structure that includes a first semiconductor layer, an intermediate layer with a light emitting layer, and a second semiconductor layer, divided into two stages. A Schottky metal layer is exposed on the surface of the low doped layer, creating a depletion region in the light emitting layer to reduce non-radiative recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mesa size is reduced to increase resolution, then the resolution is improved, but the non-radiative recombination at mesa edges increases causing lower efficiency
Solution Approach 1:
A low-doped semiconductor layer is introduced as an intermediary between the light-emitting layer and the p-type semiconductor layer. This intermediate layer extends to the mesa edge and forms a depletion region that acts as a barrier, preventing carriers from reaching the harmful mesa edge where non-radiative recombination occurs, thus protecting the light-emitting layer while maintaining the small mesa size for high resolution
Solution Approach 2:
The doping concentration is changed by introducing a low-doped layer with lower carrier concentration than the adjacent p-type layer. This parameter change creates a depletion region at the mesa edge through controlled carrier distribution, forming an energy barrier that redirects carriers away from the mesa edge and into the light-emitting layer, improving lighting efficiency while maintaining small mesa dimensions
2Shape
If etching is used to form the mesa structure, then the mesa shape is defined, but the mesa edges are damaged causing non-radiative recombination
Solution Approach 1:
The low-doped semiconductor layer serves as a protective intermediary that extends to the mesa edge, forming a depletion region that acts as a buffer zone. This intermediate structure protects the light-emitting layer from the damaged mesa edge caused by etching, allowing the etched mesa shape to be maintained while preventing harmful non-radiative recombination at the edge
3Measurement precision
If the mesa size is reduced to less than 5 μm, then the resolution is improved, but the manufacturing precision becomes more difficult to maintain
Solution Approach 1:
By changing the doping concentration parameter and introducing a low-doped layer, the patent creates a depletion region that is less sensitive to minor variations in mesa dimensions. This parameter change provides a more robust structure that maintains performance even with manufacturing variations, enabling reliable production of sub-5 μm mesas
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 the lighting efficiency of micro LEDs by reducing non-radiative recombination and improving the light extraction efficiency, leading to better performance and reduced thermal effects.
Implementation Method 1
A Schottky metal layer is disposed on the exposed surface, wherein the Schottky metal layer creates a depletion region in the light emitting layer
Implementation Method 2
Such damage may cause the micro LEDs to suffer from low efficiency due to carriers' non-radiative recombination on the mesa edges of micro LEDs
Data Source
AI summary
A micro LED element includes a mesa including a first semiconductor layer, an intermediate layer, and a second semiconductor layer stacked from top down, wherein the mesa is divided into two stages at a side of the intermediate layer, and the intermediate layer includes: a light emitting layer; and a third semiconductor layer disposed on a surface of the light emitting layer, wherein the third semiconductor layer is exposed to the outside of the mesa to have an exposed surface relative to the mesa; and a Schottky metal layer disposed on the exposed surface, wherein the Schottky metal layer creates a depletion region in the light emitting layer.