GaN LED Superlattice Doping for Current Spreading
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Solution Overview
Problem
GaN-based light emitting diodes face issues with electrostatic discharge characteristics, current leakage, and efficiency droop due to current concentration, thread dislocations, lattice mismatch, and internal fields, which affect luminous efficiency and reliability.
Innovation Solution
A light emitting diode structure with an n-type contact layer, a superlattice layer, an undoped intermediate layer, and an electron reinforcing layer is introduced, where the superlattice layer has a high silicon doping concentration only in its final layer, and the n-type contact layer includes multiple GaN and AlGaN layers to improve current spreading and reduce internal fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional n-type contact layer with uniform doping is used, then the structure is simple, but current concentration occurs leading to poor electrostatic discharge characteristics
Solution Approach 1:
The n-type contact layer is segmented into multiple sub-layers with different doping concentrations. The first n-type contact layer has a first doping concentration while the second n-type contact layer has a second doping concentration that is higher than the first. This segmentation allows current to spread more uniformly across the contact layers, preventing current concentration and improving electrostatic discharge characteristics without requiring overly complex external circuitry.
Solution Approach 2:
Different regions of the contact layer structure are assigned different doping concentrations to optimize local electrical properties. The higher doping concentration in the second n-type contact layer is strategically positioned to enhance current spreading in critical areas, while the first layer maintains a lower doping concentration to preserve other desired electrical characteristics. This local differentiation resolves the contradiction between reliability improvement and structural simplicity.
2Reliability
If high silicon doping concentration is applied throughout the superlattice layer, then current spreading is improved, but internal fields increase causing efficiency droop
Solution Approach 1:
The superlattice layer is designed with non-uniform silicon doping distribution, where only specific layers within the superlattice structure are doped with silicon while others remain undoped or lightly doped. This local quality approach enables current spreading enhancement in doped regions without creating excessive internal fields throughout the entire superlattice, thereby preventing efficiency droop while maintaining good current spreading performance.
Solution Approach 2:
The superlattice layer is segmented into multiple thin layers with alternating doped and undoped regions. This segmentation allows the doped portions to provide current spreading benefits while the undoped portions minimize internal field accumulation. The cumulative effect improves current spreading without triggering the efficiency droop that would result from uniform high doping throughout the entire superlattice structure.
3Reliability
If multiple layers with different doping concentrations are used, then current spreading and ESD resistance improve, but manufacturing complexity increases
Solution Approach 1:
The contact layer structure is segmented into a small number of discrete layers (first and second n-type contact layers) with different doping concentrations. This limited segmentation achieves the desired current spreading and ESD resistance improvement while keeping the manufacturing process manageable. The small number of layers avoids the need for complex multi-step doping processes that would be required if many more layers were used.
Solution Approach 2:
The invention changes the doping concentration parameter between the first and second n-type contact layers to achieve improved electrical performance. By adjusting this single critical parameter (doping concentration) across a limited number of layers, the invention achieves enhanced ESD resistance and current spreading without requiring changes to multiple structural parameters or complex fabrication sequences, thus maintaining ease of manufacture.
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 electrostatic discharge resistance, reduces current leakage, and lowers forward voltage, thereby improving the overall efficiency and reliability of the light emitting diode by uniformly distributing current and reducing strain and defects.
Implementation Method 1
the superlattice layer has a high silicon doping concentration only in its final layer
Implementation Method 2
the n-type contact layer includes multiple GaN and AlGaN layers to improve current spreading
Implementation Method 3
generate and emit light by recombination of electrons and holes in the quantum well layer in the active layer
Data Source
AI summary
Exemplary embodiments of the present invention disclose a light emitting diode including an n-type contact layer doped with silicon, a p-type contact layer, an active region disposed between the n-type contact layer and the p-type contact layer, a superlattice layer disposed between the n-type contact layer and the active region, the superlattice layer including a plurality of layers, an undoped intermediate layer disposed between the superlattice layer and the n-type contact layer, and an electron reinforcing layer disposed between the undoped intermediate layer and the superlattice layer. Only a final layer of the superlattice layer closest to the active region is doped with silicon, and the silicon doping concentration of the final layer is higher than that of the n-type contact layer.