InGaN LED Active Area Segmentation for Green Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
InGaN quantum wells in green LEDs suffer from alloy demixing and high stress between GaN barrier layers and InGaN quantum wells, leading to low radiative recombination rates and emission efficiency due to defect formation and low density of states.
Innovation Solution
A light emitting diode structure with a p-n junction comprising n-doped InXnGa(1-Xn)N and p-doped InXpGa(1-Xp)N layers, featuring a first and second InN layer separated by a thin InXbGa(1-Xb)N layer, with indium compositions between 0 and 0.25, allowing for high radiative recombination rates and improved emission efficiency in the green or red wavelength range without high indium concentration, thus avoiding alloy demixing and defect issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If InGaN quantum wells with high indium composition (>25%) are used to achieve green wavelength emission, then the emission wavelength is improved, but alloy demixing occurs causing defects and low radiative efficiency
Solution Approach 1:
The patent divides the single InN layer into multiple thin InN layers separated by GaN barrier layers. This segmentation allows the structure to achieve green wavelength emission through quantum confinement effects while maintaining lower indium composition in each layer, avoiding alloy demixing and improving radiative efficiency.
Solution Approach 2:
The patent creates a composite structure combining InN layers with GaN barrier layers. This composite material approach enables the system to achieve properties that neither material alone could provide: the InN layers provide the necessary bandgap for green emission while the GaN barriers prevent alloy demixing and maintain structural integrity.
2Reliability
If InN layers with very low density of states are used to reduce dislocations, then defect formation is reduced, but radiative recombination rate becomes too low for sufficient light emission
Solution Approach 1:
The patent merges multiple InN layers into a single active region separated by thin GaN barriers. This combining approach accumulates the radiative recombination capability across multiple layers while maintaining the low defect density of individual thin InN layers, achieving both low defect formation and sufficient radiative recombination rate.
Solution Approach 2:
The patent transitions from a single-layer structure to a multi-layer quantum well structure, adding the dimension of layer multiplication. This dimensional change allows the system to achieve higher overall radiative recombination rate by summing contributions from multiple layers while each layer maintains low defect density.
3Illumination intensity
If InGaN barrier layers are used to increase emission wavelength values, then green colour emission is achieved, but stress between GaN and InGaN promotes alloy demixing
Solution Approach 1:
The patent applies different material compositions locally: using pure GaN for barrier layers where mechanical stability is needed, and InN for active layers where optical performance is needed. This local quality differentiation allows the system to achieve green wavelength emission while minimizing stress-induced alloy demixing at the interfaces.
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 structure achieves a high radiative recombination rate and enhanced emission efficiency in the green or red wavelength range, with the thin separating layer enabling efficient charge carrier switching and homogenized electron distribution, resulting in better light emission efficiency compared to prior art.
Implementation Method 1
an active area arranged between the n-doped InXnGa(1-Xn)N layer and the p-doped InXpGa(1-Xp)N layer and wherein radiative recombinations are able to occur
Data Source
AI summary
A light emitting diode including an n-doped InXnGa(1-Xn)N layer and a p-doped InXpGa(1-Xp)N layer, and an active area arranged between the InXnGa(1-Xn)N layer and the InXpGa(1-Xp)N layer including: a first InN layer with a thickness eInN106; a second InN layer with a thickness eInN108; a separating layer arranged between the InN layers and including InXbGa(1-Xb)N and a thickness <3 nm; an InX1Ga(1-X1)N layer arranged between the InXnGa(1-Xn)N layer and the first InN layer; an InX2Ga(1-X2)N layer arranged between the InXpGa(1-Xp)N layer and the second InN layer; wherein the indium compositions Xn, Xp, Xb, X1 and X2 are between 0 and about 0.25, and wherein the thicknesses eInN106 and eInN108 are such that eInN106<eInN108.