GaN Light Emitting Diode with V-Shaped Quantum Wells
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Solution Overview
Problem
Semiconductor light emitting elements using group III nitride semiconductors face issues with threading dislocations on substrates, leading to defects and deteriorated light emission properties, particularly increased reverse current due to lattice misfit and V-pits formation.
Innovation Solution
A semiconductor light emitting element with a multiple quantum well structure is designed, featuring a light emitting layer with a V-shaped concave portion and specific In concentration gradients, and a manufacturing method involving alternating growth temperatures and suspension of raw material supply to reduce threading dislocation effects, resulting in improved light emission properties and reduced reverse current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gallium nitride-based semiconductor is grown on a substrate composed of a different material such as sapphire, then the semiconductor light emitting element can be manufactured, but threading dislocations and V-pits are generated due to lattice misfit, deteriorating light emission properties and increasing reverse current
Solution Approach 1:
The light emitting layer is divided into multiple quantum wells with alternating barrier layers and well layers containing In atoms. This segmentation allows the structure to accommodate threading dislocations by distributing the defect impact across multiple segments rather than having a single continuous layer vulnerable to defects.
Solution Approach 2:
The patent introduces a V-shaped concave portion in the light emitting layer with specific In concentration gradients. The In concentration on the inclined surface is controlled to be not more than 50% of the concentration in the same well layer, creating local compositional variation that addresses the defect issue locally while maintaining overall device functionality.
2Stability of the object's composition
If threading dislocations pass through laminated single crystal films, then the structural integrity is maintained, but light emission properties are largely deteriorated and reverse current is increased
Solution Approach 1:
The patent converts the harmful effect of threading dislocations into a beneficial structure by allowing V-shaped concave portions to form at defect locations. The In concentration gradient in these concave portions creates a local potential well that can trap carriers and reduce reverse current, effectively transforming the defect into a functional feature.
Solution Approach 2:
The patent changes the In concentration parameter locally in the well layers. By controlling the In concentration on the inclined surface to be not more than 50% of the concentration in the same well layer, the electronic structure is modified to reduce the impact of threading dislocations on light emission properties.
3Reliability
If a multiple quantum well structure with many well layers and barrier layers is used, then light emission properties can be improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses three or more well layers with four or more barrier layers, which is a partial implementation of multiple quantum wells. This provides sufficient light emission improvement without requiring excessive numbers of layers that would overly complicate the device structure and manufacturing process.
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 minimizes the impact of threading dislocations, enhancing light emission properties and reducing reverse current, thereby improving the overall performance of semiconductor light emitting elements.
Implementation Method 1
a light emitting layer laminated on the n-type semiconductor layer and having a multiple quantum well structure in which plural barrier layers and plural well layers containing atoms of In are alternately laminated
Implementation Method 2
a second process for laminating a light emitting layer on the n-type semiconductor layer by a metal organic chemical vapor deposition device
Data Source
AI summary
A semiconductor light emitting element includes: an n-type semiconductor layer; a light emitting layer alternately laminating plural barrier layers and plural well layers; and a p-type semiconductor layer, wherein the light emitting layer includes three or more well layers and four or more barrier layers, each well layer being sandwiched by the barrier layers, one barrier layer contacting the n-type semiconductor layer, and another barrier layer contacting the p-type semiconductor layer, the well layers include plural n-side well layers from the n-type semiconductor layer side and one p-side well layer on the p-type semiconductor layer side, and a V-shaped concave portion including inclined surfaces is generated in the light emitting layer, and in at least one of the n-side well layers, a concentration of atoms of In on the inclined surface is not more than 50% of a concentration of atoms of In in the n-side well layer.