LED Active Structure Band Gap Engineering for Reliability
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in achieving prolonged lifetime and higher reliability, particularly in maintaining light output power over extended periods under testing conditions.
Innovation Solution
The light-emitting device incorporates an active structure with well and barrier layers, where the well layers comprise InxGa1−xAs1−yPy and barrier layers comprise AlzGa1−zAs, with specific band gap differences and residual stresses to enhance carrier confinement and reduce defects, resulting in improved reliability and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LED structures are used, then manufacturing is simpler, but reliability and lifetime are reduced
Solution Approach 1:
The active structure is divided into multiple quantum well layers separated by barrier layers, creating a segmented multi-layer structure. This segmentation allows for better carrier confinement and reduced defect propagation, directly improving reliability and lifetime while managing the increased structural complexity through systematic design
Solution Approach 2:
The patent employs composite material structures combining different semiconductor layers (AlGaAs, GaAs, InGaAs) with specific band gap configurations. The composite structure of well layers and barrier layers with engineered band gaps creates superior electrical and optical properties that enhance reliability without excessive complexity
2Reliability
If well layers without phosphorus are used, then manufacturing is easier, but light output power degrades over time
Solution Approach 1:
The patent modifies the compositional parameters of the well layers by incorporating phosphorus into InGaAs material, changing the chemical composition from InxGa1−xAs to InxGa1−xAs1−yPy. This parameter change improves light output power stability by reducing defect formation and enhancing carrier confinement, while the manufacturing complexity increase is managed through controlled epitaxial growth processes
3Reliability
If band gaps are not optimized, then device structure is simpler, but carrier confinement is insufficient
Solution Approach 1:
The patent applies local quality optimization by assigning different band gap values to specific layers: the well layers have a first band gap, barrier layers have a second band gap, and intermediate layers have a third band gap, where the third band gap is between the first and second. This localized band gap engineering enhances carrier confinement at each interface while maintaining overall structural coherence
Solution Approach 2:
The patent systematically varies band gap parameters across different layers by controlling aluminum composition ratios (z1, z2, z3) in AlGaAs layers. The band gap parameters are engineered such that Eg(well) < Eg(intermediate) < Eg(barrier), creating optimal carrier confinement without excessive structural complexity
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 device maintains at least 80% of its maximum light output power after 1000 hours of reliability testing at 85°C and 85% relative humidity, significantly outperforming LEDs without phosphorus in the well layers.
Implementation Method 1
the first semiconductor layer has a first band gap, the second semiconductor layer has a second band gap, the well layer has a third band gap, and the first intermediate layer has a fourth band gap
Implementation Method 2
the active structure includes a well layer and a barrier layer
Data Source
AI summary
A light-emitting device includes an active structure, wherein the active structure includes a well layer and a barrier layer. A first semiconductor layer of first conductivity type and a second semiconductor layer of second conductivity type sandwich the active structure. A first intermediate layer is between the first semiconductor layer and the active structure, wherein the first semiconductor layer has a first band gap, the second semiconductor layer has a second band gap, the well layer has a third band gap, and the first intermediate layer has a fourth band gap, wherein the first band gap and the second band gap are both larger than the fourth band gap, and the fourth band gap is larger than the third band gap. A first window layer is on the first semiconductor layer, wherein the first intermediate layer includes Alz1Ga1−z1As, the first window layer includes Alz2Ga1−z2As, and z1>z2.