Quantum Well Band Gap Engineering for Polarization Reduction
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Solution Overview
Problem
Semiconductor light emitting devices face a challenge in minimizing the polarization effect, which degrades the recombination probability of electrons and holes due to internal field-induced spatial separation of wave functions in nitride semiconductors, affecting internal quantum efficiency.
Innovation Solution
The semiconductor light emitting device incorporates a quantum well layer structure with varying band gap energy regions, including regions with different slopes and a middle region of uniform band gap energy, to minimize the polarization effect and enhance crystallinity and internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a nitride semiconductor is grown in a polarity direction, then the device can be manufactured using standard growth processes, but a strong internal field is applied to the active layer due to polarization, causing spatial separation of electron and hole wave functions and degrading recombination probability
Solution Approach 1:
The quantum well layer is designed with non-uniform composition distribution, creating regions with different band gap energies within the same layer. This local variation in material composition allows the structure to maintain overall manufacturability while locally reducing polarization effects in specific regions where electron-hole recombination occurs.
Solution Approach 2:
The invention changes the band gap energy parameter across the quantum well layer by varying the indium content composition. By creating a gradient in composition (and thus band gap), the internal polarization field is reduced, allowing electron and hole wave functions to overlap more effectively while maintaining compatibility with standard nitride semiconductor growth processes.
2Ease of manufacture
If the band gap energy is uniformly distributed in the quantum well layer, then the structure is simple to manufacture, but the polarization effect cannot be minimized and internal quantum efficiency is degraded
Solution Approach 1:
Instead of uniform composition, the quantum well layer employs local quality variation with different indium content regions. This creates spatially varying band gap energies that reduce polarization effects in critical areas while maintaining overall structural feasibility for manufacturing.
Solution Approach 2:
The invention introduces asymmetry in the band gap distribution within the quantum well layer through non-uniform indium composition. This asymmetric composition profile is specifically designed to counteract the symmetric polarization field, reducing wave function separation and improving recombination efficiency.
3Reliability
If multiple regions with different band gap energies are introduced in the quantum well layer, then polarization influence is reduced and recombination efficiency is improved, but the device structure becomes more complex
Solution Approach 1:
The quantum well layer is designed with localized composition variations rather than completely complex multi-layer structures. By varying indium content within the well layer itself, the invention achieves polarization reduction with relatively simple structural modifications that can be implemented using standard growth techniques.
Solution Approach 2:
The invention achieves improved recombination efficiency by changing the composition parameter (indium content) within the quantum well layer rather than adding multiple complex layers. This parameter variation creates the necessary band gap gradient to reduce polarization while maintaining structural simplicity.
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 reduces the influence of polarization charges, improving electron hole recombination efficiency and maintaining carrier confinement without degrading crystallinity, resulting in enhanced internal quantum efficiency and luminous output.
Implementation Method 1
a strong field is applied to the interior of an active layer due to polarization. Thus, wave functions of electrons and holes in the active layer are spatially separated according to the generated internal field
Implementation Method 2
a semiconductor device capable of generating light of various colors according to electron hole recombination in p and n type semiconductor junction parts when current is applied thereto
Data Source
AI summary
There is provided a semiconductor light emitting device including: first and second conductivity type semiconductor layers; and an active layer disposed between the first and second conductivity type semiconductor layers and having a structure in which a plurality of quantum barrier layers and a plurality of quantum well layers are alternately disposed, wherein at least one of the plurality of quantum well layers includes a first region in which band gap energy is reduced through a first slope and a second region in which band gap energy is reduced through a second slope different from the first slope. The influence of polarization is minimized by adjusting the shape of the band gap of the quantum well layer, crystallinity and internal quantum efficiency can be enhanced.