Graded Electron Blocking Layer for LED Hole Injection
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Solution Overview
Problem
Doping larger bandgap semiconductor materials like III-nitride materials to achieve high hole concentration is difficult due to high activation energy, which affects the performance of light emitting devices such as LEDs and laser diodes.
Innovation Solution
Employing polarization enhanced doping by varying the aluminum composition in the electron blocking layer (EBL) of light emitting devices, specifically using a graded EBL with decreasing or increasing aluminum composition along certain crystallographic directions to increase hole concentration and injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If doping is used to achieve high hole concentration in III-nitride materials, then hole concentration is improved, but the process becomes difficult due to high activation energy
Solution Approach 1:
The patent introduces an electron blocking layer (EBL) as an intermediary structure between the active region and p-side heterostructure. This EBL comprises an aluminum-containing group-III-nitride alloy with graded composition that mediates carrier transport, enabling effective hole injection and electron blocking without requiring heavy doping of the III-nitride materials. The graded aluminum composition (decreasing from active region toward p-side) creates a gradual band structure transition that facilitates carrier management.
Solution Approach 2:
The patent employs parameter changes by varying the aluminum composition in the electron blocking layer. The aluminum composition is graded, decreasing as a function of distance along the [0001] direction from the active region toward the p-side heterostructure. This compositional parameter change creates a gradient in band structure that enhances hole concentration in the active region while avoiding the difficulties of direct doping.
2Quantity of substance
If constant composition EBL is used, then manufacturing is simpler, but hole concentration and injection efficiency are reduced
Solution Approach 1:
The patent applies local quality by creating a spatially varying aluminum composition within the electron blocking layer. The aluminum content is not uniform but is instead graded, with higher aluminum concentration near the active region and lower concentration toward the p-side heterostructure. This local variation in composition optimizes the electronic properties at different positions within the EBL, enhancing hole injection efficiency and electron blocking capability where needed most.
Solution Approach 2:
The patent utilizes parameter changes by implementing a graded aluminum composition profile in the EBL. The aluminum mole fraction decreases continuously or in steps as a function of distance from the active region. This parameter gradient creates favorable band alignment and polarization effects that enhance carrier injection and confinement, improving device performance despite increased structural complexity.
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 graded EBL design enhances hole concentration and injection efficiency, effectively retaining electrons in the active region for improved light emission, particularly at higher current densities, outperforming devices with constant EBL compositions.
Implementation Method 1
Employing polarization enhanced doping by varying the aluminum composition in the electron blocking layer (EBL) of light emitting devices
Implementation Method 2
an active region disposed between the p-side heterostructure and the n-side heterostructure and configured to emit light
Data Source
AI summary
A light emitting device includes a p-side heterostructure, an n-side heterostructure, an active region disposed between the p-side heterostructure and the n-side heterostructure. An electron blocking layer (EBL) disposed between the p-side heterostructure and the active region comprises an aluminum containing group-III-nitride alloy. An aluminum composition of the EBL decreases as a function of distance along a [0001] direction from the active region towards the p-side heterostructure over a majority of the thickness of the EBL.