Tensile Strained GaN Layer for Low Dislocation Nitride LEDs
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Solution Overview
Problem
Semiconductor light emitting devices using nitride semiconductors face reduced luminous efficiency due to lattice constant differences between the GaN foundation layer and the quantum well layer, leading to defects and high edge dislocation densities.
Innovation Solution
A semiconductor light emitting device is designed with a first semiconductor layer of a specific conductivity type, a light emitting layer emitting light with a peak wavelength of 440 nanometers or more, and a second semiconductor layer, where tensile strain is applied to the first semiconductor layer, and the edge dislocation density is maintained at 5×10^9/cm² or less, with a lattice mismatch factor of 0.11% or less between the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a quantum well layer using InxGa1-xN is provided on a GaN layer, then light emission is achieved, but a defect is introduced because of a lattice constant difference between the foundation GaN layer and the quantum well layer, reducing luminous efficiency
Solution Approach 1:
A tensile strained GaN layer is introduced as an intermediary layer between the foundation GaN layer and the quantum well layer. This intermediate layer has a lattice constant that is larger than the foundation GaN layer due to tensile strain, which reduces the lattice mismatch with the InxGa1-xN quantum well layer, thereby reducing defects and improving luminous efficiency
Solution Approach 2:
The lattice constant of the GaN layer is changed by applying tensile strain, transforming it from a standard lattice structure to a tensile strained structure with expanded lattice constant. This parameter change enables better lattice matching with the quantum well layer, reducing dislocation density and improving device performance
2Productivity
If the lattice constant difference between GaN layer and quantum well layer is reduced, then luminous efficiency is improved, but control of edge dislocation density becomes more critical
Solution Approach 1:
The edge dislocation density is controlled by precisely adjusting the tensile strain magnitude and the thickness of the strained GaN layer. By changing these parameters, the lattice mismatch is optimized to minimize dislocation formation while maintaining high luminous efficiency
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 configuration results in a highly efficient semiconductor light emitting device with suppressed defects, achieving high optical output and improved luminous efficiency by controlling edge dislocation density and lattice mismatch.
Implementation Method 1
a light emitting layer provided between the first semiconductor layer and the second semiconductor layer and configured to emit a light having a peak wavelength of 440 nanometers or more
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a light emitting layer provided between the first semiconductor layer and the second semiconductor layer and configured to emit a light having a peak wavelength of 440 nanometers or more. Tensile strain is applied to the first semiconductor layer. An edge dislocation density of the first semiconductor layer is 5×109/cm2 or less. A lattice mismatch factor between the first semiconductor layer and the light emitting layer is 0.11 percent or less.