Composite Quantum Well Photonic Materials for Long-Wavelength LEDs
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Solution Overview
Problem
Efficiency of InGaN-based light emitters for longer visible wavelengths remains relatively low despite achieving close to 100% external quantum efficiency in blue light emitting diodes.
Innovation Solution
Development of photonic materials comprising specific layer structures, including InyGa1-yN, (ZnaSnbGec)xGadN2, and InzGa1-zN layers, with controlled thicknesses and compositions, to enhance quantum well engineering in LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional InGaN quantum well structure is used, then the device structure is simple, but the internal quantum efficiency is low due to suppressed electron-hole wavefunction overlap
Solution Approach 1:
The patent employs a composite quantum well structure consisting of InGaN layers combined with (Zn,Sn)N2 layers. This composite structure leverages the complementary properties of both materials: InGaN provides the basic quantum well confinement while (Zn,Sn)N2 contributes to enhanced band offsets and improved electron-hole wavefunction overlap, thereby resolving the efficiency limitation of conventional single-material QWs
Solution Approach 2:
The invention introduces localized compositional variations within the quantum well structure by inserting thin (Zn,Sn)N2 layers at specific positions within the InGaN quantum well. This local modification creates regions with different band alignment characteristics that specifically address the wavefunction overlap problem without altering the entire quantum well structure
2Adaptability or versatility
If InGaN-based light emitters are designed for longer visible wavelengths, then the emission wavelength range is extended, but the efficiency decreases due to internal electric fields and charge separation
Solution Approach 1:
The patent modifies the compositional parameters of the quantum well structure by incorporating varying ratios of Zn and Sn in the (Zn,Sn)N2 layers, and adjusting the In composition in InGaN layers. These parameter changes enable tuning of the bandgap and emission wavelength while simultaneously optimizing the band alignment to maintain high efficiency across the green and amber wavelength ranges
Solution Approach 2:
The composite structure of InGaN/(Zn,Sn)N2/InGaN quantum wells addresses the efficiency-wavelength tradeoff by combining materials with different bandgap characteristics. The (Zn,Sn)N2 layers provide appropriate band offsets that confine carriers effectively even at longer wavelengths where internal electric fields and charge separation typically suppress efficiency
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
Improves the efficiency of LED designs by increasing spontaneous emission recombination rates and peak wavelength coverage for visible light emission.
Implementation Method 1
utilizing pulsed MOCVD growth to achieve high crystalline quality and large band offsets, enhancing electron-hole wavefunction overlap and confinement
Data Source
AI summary
Disclosed herein are photonic materials. The photonic materials comprise a first layer, a second layer, and a third layer, wherein the second layer is disposed between and in contact with the first layer and the third layer, such that the second layer is sandwiched between the first layer and the third layer. In some examples, the first layer comprises InyGa1-yN, wherein y is from 0 to 0.8. In some examples, the second layer comprises (ZnaSnbGec)xGadN2, wherein: x is from greater than 0 to 1; a, b, c, and d are each independently from 0 to 1; with the proviso that at least one of a, b, or c is greater than 0. In some examples, the third layer comprises InzGa1-zN, wherein z is from 0 to 0.8.