Nitride Semiconductor Barrier Thickness Profile for Light Emission
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Solution Overview
Problem
Semiconductor light emitting devices with nitride group materials face challenges in achieving high light emission efficiency due to dislocations and crystal defects, which also increase serial-connection resistance and forward voltage, making it difficult to achieve efficient light emission.
Innovation Solution
The design involves varying the thickness and composition of barrier and well layers in the active region, with thinner barrier layers on the p-type semiconductor side and thicker ones on the n-type side, and using a cap layer to prevent indium departure, which improves crystallinity and reduces serial resistance, thereby enhancing light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of well layer is increased or the number of deposited well layers is increased to provide high intensity light emission, then light emission intensity is improved, but dislocations and crystal defects increase causing reduced light emission efficiency
Solution Approach 1:
The patent applies local quality by varying the thickness of barrier layers at different locations within the active layer. Specifically, the barrier layer thickness is increased in regions where dislocations are more likely to propagate (such as near defect sources or in high-stress areas), while maintaining thinner barriers in regions where defects are less problematic. This localized adjustment of barrier layer thickness allows the structure to suppress dislocation propagation where needed without unnecessarily increasing overall layer thickness, thereby maintaining high light emission efficiency while achieving high intensity emission through multiple well layers.
2Illumination intensity
If the thickness of well layer is increased or the number of deposited well layers is increased to provide high intensity light emission, then light emission intensity is improved, but serial-connection resistance increases causing increased forward voltage
Solution Approach 1:
The patent implements local quality by creating spatial variation in barrier layer thickness within the active layer structure. Thinner barrier layers are positioned in regions where reduced resistance is critical (such as in series connection paths), while thicker barriers are placed where dislocation suppression is the primary concern. This localized thickness modulation allows the structure to reduce serial-connection resistance and forward voltage in specific areas without compromising the overall dislocation suppression capability, thereby enabling high intensity light emission with lower energy loss.
3Reliability
If barrier layer thickness is increased to suppress dislocations, then light emission efficiency is improved, but serial-connection resistance increases causing increased forward voltage
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatially varying barrier layer thickness. In regions where dislocation suppression is most critical (such as near the n-type contact layer or in areas with high defect density), thicker barrier layers are used to maintain high light emission efficiency. In contrast, in regions where serial connection paths exist or where dislocation pressure is lower, thinner barrier layers are employed to reduce resistance and forward voltage. This localized differentiation allows simultaneous optimization of both light emission efficiency and electrical resistance characteristics.
Solution Approach 2:
The patent employs asymmetry by creating an asymmetric thickness profile for barrier layers within the active layer structure. Rather than using uniform thickness throughout, the barrier layers exhibit deliberate thickness variations - with some portions being thicker and others thinner - creating an asymmetric structure that optimizes different regions for different functions (dislocation suppression versus resistance reduction). This asymmetric design enables the structure to achieve both high light emission efficiency and low forward voltage simultaneously.
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 effectively suppresses the reduction in light emission efficiency caused by dislocations and crystal defects, leading to improved light emission efficiency and reduced forward voltage, resulting in a more efficient nitride group semiconductor light emitting device.
Implementation Method 1
the thicknesses of the barrier layers that are located on the p-type semiconductor layer side are smaller than the barrier layers that are located on the n-type semiconductor layer side... the crystallinity can be improved... suppress reduction of light emission efficiency resulting from dislocations or crystal defects
Implementation Method 2
using a cap layer to prevent indium departure, which improves crystallinity
Implementation Method 3
Semiconductor light emitting devices that include a light emitting layer between p-type and n-type semiconductor layers have been practically used as light emitting diodes (LED)... these semiconductor light emitting devices have been energetically researched and developed
Data Source
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AI summary
A nitride group semiconductor light emitting device includes a substrate (4), n-type and p-type semiconductor layers (11, 12), and an active region (13). The n-type and p-type semiconductor layers (11, 12) are formed on or above the substrate. The active region (13) is interposed between the n-type and p-type semiconductor layers (11, 12). The active region (13) includes barrier layers (2) that are included in a multiquantum well structure, and an end barrier layer (15) that has a thickness greater than the barrier layer, and is arranged closest to the p-type semiconductor layer (12). The average thickness of the last two barrier layers that are arranged adjacent to the end barrier layer (15) is smaller than the average thickness of the other barrier layers among the thicknesses of the barrier layers that are included in the multiquantum well structure.