UV LED Intermediate Layer for Hole Injection
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Solution Overview
Problem
Ultraviolet light emitting diodes (UV LEDs) face challenges in increasing luminance and luminous efficacy due to high activation energy for Mg-H complex dissociation, reduced hole density in p-regions, increased contact resistance at semiconductor layer boundaries, and elevated operation voltage, particularly in UV light emitting devices with high Al composition ratios.
Innovation Solution
A UV LED structure is designed with a first semiconductor layer doped with n-type dopants, an active layer of InxAlyGa1-x-yN with multiple barrier and well layers, an intermediate layer of InaAlbGa1-a-bN with reduced bandgap energy, and a blocking layer of InzAlwGa1-z-wN with higher bandgap energy, all optimized to enhance hole injection and recombination efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the Al composition ratio in the semiconductor layer is increased to produce ultraviolet light, then the light emission wavelength shifts to ultraviolet range, but the activation energy for Mg-H complex dissociation increases and hole density decreases
Solution Approach 1:
An intermediate layer with moderate Al composition (5-20%) is introduced between the active layer and the p-type semiconductor layer. This intermediate layer acts as a mediator that reduces the activation energy barrier for hole injection compared to high Al composition layers, while still maintaining compatibility with the ultraviolet light emission requirements. The intermediate layer facilitates Mg-H complex dissociation and hole generation without the severe penalties of high Al content.
Solution Approach 2:
The patent optimizes the Al composition ratio in the intermediate layer to be specifically 5-20%, which is lower than conventional designs. This parameter change reduces the activation energy for Mg-H complex dissociation while maintaining sufficient hole density. The thickness is also optimized to 1-50 nm to achieve the desired balance between hole injection efficiency and electrical properties.
2Illumination intensity
If the Al composition ratio is increased, then ultraviolet light emission is achieved, but contact resistance at the semiconductor layer boundary surface increases
Solution Approach 1:
The Al composition ratio in the intermediate layer is reduced to 5-20%, which directly lowers the contact resistance at the boundary surface between the intermediate layer and the p-type semiconductor layer. This parameter optimization maintains ultraviolet light emission capability while significantly improving electrical contact properties.
Solution Approach 2:
The intermediate layer serves as a transition layer with moderate Al composition that mediates the interface between the active layer and the p-type semiconductor layer. This intermediate structure reduces contact resistance by providing a gradual compositional transition, avoiding the abrupt interface issues that occur with direct high Al composition contacts.
3Illumination intensity
If the Al composition ratio is increased, then ultraviolet light emission is achieved, but operation voltage increases
Solution Approach 1:
By optimizing the Al composition ratio in the intermediate layer to 5-20% and thickness to 1-50 nm, the patent reduces the operation voltage of the UV LED. The lower Al content reduces the activation energy barriers and improves carrier injection efficiency, thereby lowering the voltage required for operation while maintaining ultraviolet light emission.
4Illumination intensity
If the Al composition ratio is increased, then ultraviolet light emission is achieved, but luminous efficacy decreases
Solution Approach 1:
The patent optimizes the Al composition ratio in the intermediate layer to 5-20%, which improves luminous efficacy by enhancing hole injection efficiency and reducing non-radiative recombination losses. The optimized composition and thickness parameters ensure that more electrical energy is converted into useful ultraviolet light rather than being lost as heat or other forms of energy.
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 proposed structure improves luminous efficacy by increasing hole injection and reducing current leakage, while also lowering operation voltage and contact resistance, thereby enhancing the overall performance of UV LEDs.
Implementation Method 1
it has been difficult to increase injection probability of holes into an active layer due to high piezoelectric polarization
Implementation Method 2
A light emitting diode (LED) as a representative example of a light emitting device is a device which converts electrical signals into infrared light, visible light or ultraviolet light
Data Source
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AI summary
Disclosed is a light emitting diode (100) including a first semiconductor layer (120) doped with an n-type dopant, a second semiconductor layer doped (150) with a p-type dopant, an active layer (130) disposed between the first semiconductor layer (120) and the second semiconductor layer (150), the active layer (130) being formed of InxAlyGa1-x-yN (0≤x≤1, 0≤y≤1, 0≤x+y≤1) and including a plurality of barrier layers (B1, B2, B3) and a plurality of well layers (Q1, Q2, Q3), the well layers being interposed between the barrier layers and having a smaller bandgap energy than that of the barrier layers, an intermediate layer (180) interposed between the active layer (130) and the second semiconductor layer (150), the intermediate layer being formed of InaAlbGa1-a-bN (0≤a≤1, 0≤b≤1, 0≤a+b≤1) and having a smaller bandgap energy than that of the barrier layers (B1, B2, B3), and a blocking layer (140) disposed between the intermediate layer (180) and the second semiconductor layer (150), the blocking layer being formed of InzAlwGa1-z-wN (0≤z≤1, 0≤w≤1, 0≤z+w≤1) and having a greater bandgap energy than that of each of the barrier layers and the intermediate layer.