III-Nitride Light Emitting Device Strain-Relieved Layer
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Solution Overview
Problem
Semiconductor light emitting devices face strain-related issues due to lattice mismatch between III-nitride layers and substrates, leading to defects and reduced quantum efficiency, especially when growing thicker light emitting layers, which limits their performance at high current densities and increases the risk of spinodal decomposition.
Innovation Solution
The introduction of a strain-relieved layer that expands laterally to relax strain, allowing the growth of thicker light emitting layers with reduced defects and increased critical thickness, achieved by configuring the growth surface to accommodate lateral expansion, such as using textured surfaces or semiconductor posts, which increases the in-plane lattice constant and reduces strain in the light emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thicker light emitting layers are grown to reduce carrier density and improve quantum efficiency at high current densities, then quantum efficiency is improved, but strain in the layer increases leading to defects and spinodal decomposition
Solution Approach 1:
The light emitting layer is divided into multiple quantum wells separated by barrier layers. This segmentation allows the total thickness needed for reduced carrier density to be achieved while keeping individual quantum well thicknesses below the critical strain thickness, preventing defects and spinodal decomposition.
Solution Approach 2:
Barrier layers are introduced as intermediary structures between quantum wells. These barrier layers with different composition and lattice constants serve as strain management interfaces, allowing the overall structure to achieve the necessary total thickness while managing strain through the intermediary barrier regions.
2Productivity
If the light emitting layer thickness is increased to reduce charge carrier density and nonradiative recombination, then external quantum efficiency increases, but growth becomes difficult due to strain limitations
Solution Approach 1:
The light emitting layer is segmented into multiple quantum wells separated by barrier layers. This allows the structure to achieve greater total thickness for improved quantum efficiency while each segment remains thin enough to be grown without excessive strain, making manufacturing feasible.
Solution Approach 2:
The composition parameters of the light emitting layer are changed by creating alternating regions of different InN composition (quantum wells with higher In content for emission, barrier layers with lower In content). This parameter variation allows achieving the desired total thickness and optical properties while managing strain through composition modulation.
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 approach enables the growth of thicker light emitting layers with lower defect densities and reduced spinodal decomposition, enhancing the quantum efficiency and operational stability of III-nitride light emitting devices, particularly at higher current densities and longer wavelengths.
Implementation Method 1
the strain-relieved layer grows only on portions of the surface, providing space for the strain-relieved layer to expand laterally and at least partially relax
Data Source
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AI summary
In accordance with embodiments of the invention, strain is reduced in the light emitting layer of a Ill-nitride device by including a strain-relieved layer in the device. The surface on which the strain-relieved layer is grown is configured such that strain-relieved layer can expand laterally and at least partially relax. In some embodiments of the invention, the strain-relieved layer is grown over a textured semiconductor layer or a mask layer. In some embodiments of the invention, the strain-relieved layer is group of posts of semiconductor material.