AlGaInN Protective Layer for Group III Nitride LED Emission
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Solution Overview
Problem
The existing MQW structure in Group III nitride semiconductor light-emitting devices experiences reduced emission performance due to In evaporation from the well layer during barrier layer growth, and the use of AlGaN protective layers at the same growth temperature results in low crystal quality and carrier trapping.
Innovation Solution
A Group III nitride semiconductor light-emitting device with a MQW structure featuring a well layer, a protective layer of AlGaInN with an In composition ratio of 0% to 4%, and a barrier layer of AlGaN, where the protective layer's In composition ratio is 1.5% to 3.5% and has a layered structure with a GaN second protective layer, improving crystallinity and carrier confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is provided between the well layer and barrier layer to prevent In evaporation, then emission performance is improved, but the protective layer exhibits low crystal quality and causes carrier trapping when grown at the same temperature as the well layer
Solution Approach 1:
The protective layer is grown at the same temperature as the well layer (isothermal growth) by adjusting the growth conditions, thereby preventing In evaporation while maintaining good crystal quality. This resolves the contradiction by changing the growth parameter conditions rather than simply increasing temperature.
Solution Approach 2:
The protective layer uses an AlGaInN composite material composition that combines the benefits of AlGaN (protection against In evaporation) with In incorporation (improved crystal quality and reduced carrier trapping). This composite approach allows the protective layer to function effectively at lower temperatures.
2Loss of substance
If the protective layer is made of AlGaN to prevent In evaporation, then In retention is improved, but carrier confinement effect is reduced and carriers are trapped in the protective layer
Solution Approach 1:
By incorporating a small amount of In (0% < x ≤ 4%) into the AlGaN protective layer to form AlGaInN, the crystal quality is improved and carrier trapping is reduced while still maintaining the protective function against In evaporation. The In composition ratio is carefully controlled to balance these competing requirements.
3Loss of substance
If the protective layer thickness is increased to improve protection, then In evaporation prevention is improved, but carrier recombination and trapping in the protective layer increase
Solution Approach 1:
The protective layer thickness is optimized to a specific range (0.2 nm to 1.8 nm) that provides sufficient protection against In evaporation while minimizing carrier recombination and trapping. This optimal thickness balances the protective function with the requirement to maintain high emission performance.
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 enhances emission performance by reducing carrier recombination and trapping in the protective layer, improving light intensity and crystallinity while maintaining the benefits of In as a surfactant, thus overcoming the limitations of previous protective layer designs.
Implementation Method 1
In is evaporated from the well layer due to heating up, thereby causing reduction in emission performance or variation in emission wavelength. Therefore, a protective layer is provided between the well layer and the barrier layer, which is grown at the same temperature as the growth temperature of the well layer, thereby preventing the evaporation of In.
Implementation Method 2
the protective layer comprises a first protective layer formed of AlGaInN having a bandgap larger than that of the well layer and an In composition ratio of more than 0% and not more than 4%. Such a composition of the protective layer reduces the pits in the protective layer due to the effect of In as a surfactant, and increases the crystallinity, thereby improving emission performance.
Data Source
AI summary
The present invention provides a Group III nitride semiconductor light-emitting device exhibiting improved emission performance. A light-emitting layer has a MQW structure in which a plurality of layer units are repeatedly deposited, each layer unit comprising a well layer, a protective layer, and a barrier layer sequentially deposited. The protective layer has a layered structure comprising a second protective layer disposed in contact with and on the well layer, and a first protective layer disposed in contact with and on the second protective layer. The second protective layer is formed of GaN. The first protective layer is formed of AlGaInN. The first protective layer has a bandgap larger than that of the well layer and not larger than that of the barrier layer. Moreover, the first protective layer has an In composition ratio of more than 0% and not more than 4%.