GaN LED P-type Layer Segmentation for Hole Injection and Impurity Control
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Solution Overview
Problem
The efficiency of light emitting diodes (LEDs) using GaN-based compound semiconductors is limited by impurities from the P-type semiconductor layer diffusing into the active layer, forming electron traps and reducing luminous efficiency, and hydrogen combining with Mg, which decreases hole production and mobility.
Innovation Solution
An improved laminated structure for the P-type semiconductor layer is introduced, comprising a P-type clad layer, a hole injection layer, and a P-type contact layer, with controlled doping concentrations and bandgaps, and undoped layers to prevent impurity diffusion and hydrogen combination, enhancing hole injection and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a P-type semiconductor layer is used to inject holes into the active layer, then hole injection is improved, but impurities from the P-type layer diffuse into the active layer forming electron traps and reducing luminous efficiency
Solution Approach 1:
The P-type semiconductor layer is divided into multiple sub-layers with different doping concentrations and compositions. The P-type clad layer has lower doping concentration to reduce impurity diffusion, while the P-type contact layer has higher doping concentration to ensure good electrical contact. This segmentation allows each layer to perform its specific function optimally without compromising the active layer.
Solution Approach 2:
Different regions of the P-type semiconductor layer are given different local properties through varying doping concentrations and material compositions. The P-type clad layer adjacent to the active layer has low doping to prevent impurity diffusion, while the P-type contact layer has high doping for electrical contact. This local quality optimization resolves the contradiction between hole injection and impurity prevention.
2Reliability
If ammonia is introduced to prevent epitaxial layer decomposition, then crystal quality is maintained, but hydrogen combines with Mg to reduce hole production and mobility
Solution Approach 1:
An undoped barrier layer is deposited between the P-type clad layer and the active layer before introducing ammonia. This preliminary action creates a protective barrier that prevents hydrogen from reaching and combining with Mg in the P-type layer, thereby maintaining hole production and mobility while still allowing ammonia to protect the epitaxial layer.
Solution Approach 2:
The undoped barrier layer acts as an intermediary between the ammonia-containing environment and the Mg-doped P-type layer. It mediates the interaction by blocking hydrogen diffusion while allowing the beneficial effects of ammonia to reach the epitaxial layer, thus resolving the contradiction between layer stability and hole mobility.
3Productivity
If doping concentration in the P-type layer is increased to improve hole production, then hole injection is enhanced, but impurity diffusion into the active layer increases
Solution Approach 1:
The P-type semiconductor layer is segmented into multiple layers with different doping concentrations. The P-type contact layer has high doping concentration to ensure good electrical contact and facilitate hole injection, while the P-type clad layer has lower doping concentration to minimize impurity diffusion into the active layer. This segmentation allows high hole production without excessive impurity diffusion.
Solution Approach 2:
Different doping concentrations are applied locally to different regions of the P-type semiconductor layer. The contact layer has high doping for electrical performance, while the clad layer has lower doping to protect the active layer from impurity diffusion. This local quality differentiation resolves the contradiction between hole production and impurity prevention.
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 structure increases the recombination rate of electrons and holes, improves internal quantum efficiency, and prevents non-light emitting recombination by reducing impurity diffusion, thereby enhancing luminous efficiency and hole production.
Implementation Method 1
Electrons and holes are injected into the active layer from the N-type and P-type semiconductor layers, respectively
Implementation Method 2
the electrons and holes are recombined in the active layer, thereby emitting light
Implementation Method 3
impurities from the P-type semiconductor layer are diffused into the active layer
Implementation Method 4
hydrogen contained in the ammonia is combined with a P-type impurity, e.g., Mg to prevent Mg from being activated
Data Source
AI summary
Disclosed is a light emitting diode (LED) with an improved structure. The LED comprises an N-type semiconductor layer, a P-type semiconductor layer and an active layer interposed between the N-type and P-type semiconductor layers. The P-type compound semiconductor layer has a laminated structure comprising a P-type clad layer positioned on the active layer, a hole injection layer positioned on the P-type clad layer, and a P-type contact layer positioned on the hole injection layer. Accordingly, holes are more smoothly injected into the active layer from the P-type semiconductor layer, thereby improving the recombination rate of electrons and holes.