Nitride Semiconductor Light Emitting Device Strain Control
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Solution Overview
Problem
Nitride-based semiconductor light emitting devices, particularly those emitting ultraviolet light with wavelengths of 365 nm or less, suffer from poor luminous efficiency due to internal electric fields and spatial disagreements between electron and hole wave functions in the AlGaN/AlGaInN multi-quantum well structure, reducing the number of electrons and holes involved in the light-emitting process.
Innovation Solution
Incorporating a strain control layer with an energy band gap greater than that of the quantum well layer within the active layer, formed of AlxInyGa1-x-yN materials, to reduce internal electric fields and align the spatial distribution of electron and hole wave functions, thereby increasing recombination rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an AlGaN/AlGaInN multi-quantum well structure is used to achieve ultraviolet light emission with wavelength of 365 nm or less, then the emitting wavelength requirement is met, but the luminous efficiency deteriorates due to internal electric fields and spatial disagreement between electron and hole wave functions
Solution Approach 1:
A strain control layer is introduced as an intermediary component between the quantum well layer and quantum barrier layers. This strain control layer has a lattice constant and energy band gap specifically designed to be intermediate between the AlGaN quantum barrier layer and AlGaInN quantum well layer, thereby reducing the lattice mismatch and internal electric fields while maintaining the ultraviolet emission wavelength of 365 nm or less
Solution Approach 2:
The energy band gap of the strain control layer is carefully controlled to satisfy the relationship: energy band gap of quantum well layer < energy band gap of strain control layer < energy band gap of quantum barrier layer. This parameter optimization allows the strain control layer to reduce internal electric fields and improve spatial agreement of wave functions without sacrificing the ultraviolet emission characteristics
2Illumination intensity
If the quantum well layer is designed to emit ultraviolet light with wavelength of 365 nm or less, then the emitting wavelength is achieved, but the spatial distribution of electron and hole wave functions disagrees, reducing the number of electrons and holes involved in light-emitting process
Solution Approach 1:
The strain control layer acts as a mediator that reduces lattice mismatch between the AlGaN quantum barrier layer and AlGaInN quantum well layer. By controlling the lattice constant and energy band gap of the strain control layer to be intermediate between these two layers, the spatial distribution of electron and hole wave functions is improved, increasing the number of carriers involved in radiative recombination while maintaining ultraviolet emission at 365 nm or less
3Productivity
If a multi-quantum well structure is used to improve luminous efficiency per current, then the internal quantum efficiency is enhanced, but the internal electric field causes bending of energy band and reduces electron-hole recombination probability
Solution Approach 1:
The energy band gap of the strain control layer is optimized to satisfy: energy band gap of quantum well layer < energy band gap of strain control layer < energy band gap of quantum barrier layer. This parameter control reduces the internal electric field and energy band bending in the multi-quantum well structure, thereby improving electron-hole spatial overlap and recombination probability while maintaining high luminous efficiency per current
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 strain control layer enhances luminous efficiency by reducing internal electric fields and improving the spatial agreement of electron and hole wave functions, leading to increased recombination rates and improved light-emitting performance.
Implementation Method 1
at least one strain control layer having an energy band gap greater than that of a quantum well layer of an active layer is formed in the quantum well layer in order to enhance the luminous efficiency by reducing an internal electric field
Implementation Method 2
The active layer is a region where electrons and holes are recombined, and has a structure that a quantum well layer is disposed between quantum barrier layers
Implementation Method 3
a bending of energy band is caused by a difference in lattice constant between the quantum barrier layer of AlGaN and the quantum well layer of AlGaInN
Data Source
AI summary
The disclosure relates to a nitride based semiconductor light emitting device with improved luminescence efficiency by increasing a recombination rate of electrons and holes contributing to luminescence, which results from matching the spatial distribution of electron and hole wave functions. The nitride based semiconductor light emitting device according to the present invention includes an n-type nitride layer, an active layer formed on the n-type nitride layer, and a p-type nitride layer formed on the active layer. At this stage, a strain control layer, and the at least one layer has a larger energy bandgap than a quantum well layer in the active layer. The strain control layer is disposed in an area where the quantum well layer of the active layer is formed. Moreover, an energy bandgap of the strain control layer is less than that of quantum barrier of the active layer.