LED Hole Diffusion Layer Structure for Current Crowding Relief
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Solution Overview
Problem
P-type semiconductor in LEDs experiences current crowding, leading to increased turn-on voltage and decreased luminous efficiency.
Innovation Solution
Incorporating a hole diffusion layer with undoped AlN, AlInGaN, or AlGaN sub-layers between the light-emitting layer and the P-type semiconductor layer to diffuse holes evenly, reducing current crowding and improving luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional P-type semiconductor layer is used in the LED, then the device structure is simple, but current crowding occurs resulting in increased turn-on voltage and decreased luminous efficiency
Solution Approach 1:
The P-type semiconductor layer is segmented into multiple sub-layers with different doping concentrations. The first P-type sub-layer has a first doping concentration while the second P-type sub-layer has a second doping concentration that is lower than the first. This segmentation creates a doping concentration gradient that effectively diffuses current and reduces current crowding, thereby improving luminous efficiency without significantly complicating the device structure.
2Reliability
If the P-type semiconductor layer is doped to improve hole concentration, then hole injection is enhanced, but current crowding worsens and turn-on voltage increases
Solution Approach 1:
Different regions of the P-type semiconductor layer are assigned different doping concentrations to achieve local optimization. The first P-type sub-layer closer to the active region has a higher doping concentration to ensure sufficient hole injection, while the second P-type sub-layer has a lower doping concentration to reduce current crowding and lower turn-on voltage. This local quality variation resolves the contradiction between hole injection and power consumption.
3Ease of manufacture
If a single-layer P-type semiconductor structure is used, then manufacturing is simple, but current diffusion is poor leading to reduced luminous efficiency
Solution Approach 1:
The P-type semiconductor layer is divided into multiple sub-layers with progressively decreasing doping concentrations from the active region outward. This segmented structure enhances current diffusion capability and luminous efficiency while maintaining compatibility with existing manufacturing processes, as each sub-layer can be grown sequentially using standard epitaxial techniques.
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 solution effectively reduces turn-on voltage and enhances brightness by preventing holes from concentrating in specific paths, thereby improving current diffusion and overall efficiency.
Implementation Method 1
a hole diffusion layer, and a P-type semiconductor layer sequentially stacked in that order... by adding the hole diffusion layer between the light-emitting layer and the P-type semiconductor layer, a particular structure of the hole diffusion layer can change paths of holes to prevent the holes from being crowded in the same position, thereby achieving the effect of current diffusion
Data Source
AI summary
A light-emitting diode includes an N-type semiconductor layer, a light-emitting layer, a first P-type semiconductor layer, a hole diffusion layer and a second P-type semiconductor layer sequentially stacked in that order. The hole diffusion layer includes a first sub-layer, a second sub-layer and a third sub-layer sequentially stacked along a direction from the first P-type semiconductor layer to the second P-type semiconductor layer. The first sub-layer is an AlN layer, the second sub-layer is an AlInGaN layer or an AlGaN layer, and the third sub-layer is an AlInGaN layer or an AlGaN layer. As a result, advantages of alleviating a current crowding problem and improving luminous efficiency can be achieved.