Light emitting element
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Solution Overview
Problem
The diffusion of p-type impurity from the tunnel-junction-forming p-type layer towards the second active layer side leads to a reduced output in light emitting elements with a tunnel junction.
Innovation Solution
A light emitting element structure is designed with a first intermediate layer positioned between the second active layer and the tunnel junction, which reduces the diffusion of p-type impurity, thereby maintaining crystalline quality and enhancing light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tunnel junction is formed using high impurity concentration semiconductor layers, then the tunnel junction functionality is achieved, but p-type impurity diffusion towards the active layer occurs reducing light output
Solution Approach 1:
A first intermediate layer is introduced between the tunnel junction structure and the second active layer. This intermediate layer acts as a barrier to prevent p-type impurity diffusion from the tunnel junction towards the active layer, while allowing the tunnel junction to maintain its high impurity concentration structure for proper functionality. The intermediate layer thus mediates between the conflicting requirements of tunnel junction performance and light output preservation.
Solution Approach 2:
The semiconductor structure is segmented into distinct functional regions: the tunnel junction region with high impurity concentration, the intermediate layer region with graded impurity concentration, and the active layer region. This segmentation allows each region to be optimized independently - the tunnel junction for its electrical functionality and the active layer for light emission, with the intermediate layer serving as a transition zone.
2Object-affected harmful factors
If the distance between the tunnel junction and active layer is increased to prevent impurity diffusion, then impurity diffusion is reduced, but the device structure becomes more complex
Solution Approach 1:
Rather than simply increasing the distance between the tunnel junction and active layer, an intermediate layer is inserted as a mediator. This layer has specific properties (lower impurity concentration than the tunnel junction) that actively prevent impurity diffusion while maintaining a compact overall device structure. The intermediate layer provides a functional solution that is more efficient than merely increasing physical separation.
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 intermediate layer increases the distance between the active layer and the tunnel-junction-forming p-type layer, preventing impurity diffusion and improving the light output of the light emitting element.
Implementation Method 1
Diffusion of p-type impurity from a tunnel-junction-forming p-type layer towards the second active layer side is believed to be one of the causes of a reduced output of a light emitting element having a tunnel junction
Data Source
AI summary
A light emitting element comprises a first n-side semiconductor layer, a first active layer having a first well layer containing indium, a first p-side semiconductor layer, a second n-side semiconductor layer in contact with the first p-side semiconductor layer, a second active layer having a second well layer containing indium, and a second p-side semiconductor, each formed of a nitride semiconductor. The second active layer has a first intermediate layer positioned closer to the first active layer than is the second well layer and containing indium. An indium composition ratio of the first well layer is less than an indium composition ratio of the second well layer. An indium composition ratio of the first intermediate layer is less than an indium composition ratio of the first well layer. A thickness of the first intermediate layer is less than a thickness of the second well layer.