Graded Al Composition in III-P LED Interfaces
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Solution Overview
Problem
Conventional AlGaInP LEDs face challenges with high forward voltage (Vf) due to energy barriers at interfaces, particularly between the window layer and device layers, which affects efficiency and power consumption.
Innovation Solution
Incorporating graded composition regions between the p-type region and the GaP window layer, and optionally between the etch stop layer and the n-type region, to smooth out energy barriers and reduce Vf, with specific grading profiles in the Al composition to optimize light emission wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional AlGaInP LED structure with abrupt interfaces is used, then the device structure is simple and easy to manufacture, but the forward voltage is high due to energy barriers at interfaces
Solution Approach 1:
The patent applies parameter changes by gradually varying the aluminum composition in the graded regions between the active layer/window layer and etch stop layer/confining layer interfaces. This continuous parameter change smooths the energy band discontinuities, reducing the forward voltage drop at these interfaces while maintaining the overall device structure.
Solution Approach 2:
The patent implements local quality by introducing graded composition regions specifically at the critical interfaces where energy barriers form, while keeping other parts of the device structure conventional. This targeted approach reduces forward voltage at specific locations without requiring complex changes throughout the entire device.
2Loss of energy
If graded composition regions are introduced to reduce forward voltage, then power efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The graded composition regions are formed by continuously varying the aluminum content during epitaxial growth, which reduces energy barriers and forward voltage, thereby improving power efficiency. The gradual parameter change enables better carrier transport across interfaces.
Solution Approach 2:
The graded regions are incorporated during the initial epitaxial growth process, performing the composition grading action in advance during manufacturing. This preliminary action embeds the energy barrier reduction functionality directly into the device structure during fabrication, rather than requiring post-processing modifications.
3Reliability
If aluminum composition is graded in the graded region, then internal quantum efficiency is enhanced, but the composition control difficulty increases
Solution Approach 1:
The patent applies local quality by implementing aluminum composition grading specifically in the graded regions adjacent to interfaces, where it is most needed to reduce energy barriers and enhance internal quantum efficiency. The grading profiles are tailored to local requirements at each interface.
Solution Approach 2:
The continuous variation of aluminum composition in the graded regions modifies the energy band structure locally, reducing interface energy barriers and improving carrier recombination efficiency. This parameter change enhances internal quantum efficiency by facilitating better carrier transport and reducing non-radiative recombination at interfaces.
Data Source
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AI summary
One or more regions of graded composition are included in a III-P light emitting device, to reduce the V f associated with interfaces in the device. In accordance with embodiments of the invention, a semiconductor structure comprises a III-P light emitting layer disposed between an n-type region and a p-type region. A graded region is disposed between the p-type region and a GaP window layer. The aluminum composition is graded in the graded region. The graded region may have a thickness of at least 150 nm. In some embodiments, in addition to or instead of a graded region between the p-type region and the Ga P window layer, the aluminum composition is graded in a graded region disposed between an etch stop layer and the n-type region.