LED Quantum Well Sidewall Treatment for Small-Size Efficiency
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Solution Overview
Problem
The quantum efficiency of light-emitting diodes (LEDs) with small lateral dimensions decreases due to degradation of semiconductor material during etching, leading to parasitic recombination phenomena at the LED sides, which reduces their efficiency.
Innovation Solution
A chemical treatment is applied to selectively etch a component of the semiconductor alloy on the lateral walls of the LED trenches, reducing the indium concentration in the peripheral areas, thereby widening the bandgap and diverting charge carriers away from degraded regions, and a trench is formed using dry etching methods like RIE or ICP etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a trench is formed by etching to singularize the LED, then the LED can be individually addressed and packaged, but the semiconductor material at the lateral walls undergoes degradation leading to parasitic recombination
Solution Approach 1:
The patent applies local quality by creating a compositional gradient within the quantum well structure. The semiconductor alloy composition is intentionally varied spatially, with different indium concentrations at different radial positions from the LED center. This local compositional variation allows the peripheral regions to have different optical and electrical properties compared to the central region, specifically addressing the parasitic recombination issue at the edges while maintaining high efficiency in the center.
Solution Approach 2:
The patent employs parameter changes by systematically varying the indium concentration parameter across the quantum well composition. By controlling the indium content to decrease from the center toward the periphery, the bandgap energy is locally adjusted. This parameter variation optimizes the balance between light emission efficiency in the central region and reduced parasitic recombination at the peripheral regions affected by etching degradation.
2Productivity
If the LED lateral dimensions are reduced to increase device density, then more LEDs can be packaged in a given area, but quantum efficiency decreases due to increased relative impact of etching degradation
Solution Approach 1:
For small-lateral-dimension LEDs, the local quality principle becomes even more critical. The compositional gradient is particularly important in miniaturized devices where the peripheral-to-total area ratio is higher. By implementing the indium concentration gradient, the patent ensures that even in small LEDs, the central emission region maintains optimal composition while the peripheral regions with higher relative impact from etching have compositional characteristics that reduce parasitic recombination.
Solution Approach 2:
The parameter changes approach allows optimization of quantum efficiency across different LED size scales. The indium concentration profile is designed to compensate for the increased relative impact of edge effects in smaller devices, enabling high device density packaging while maintaining acceptable quantum efficiency even in miniaturized LEDs where the perimeter-to-area ratio is maximized.
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 significantly decreases parasitic recombinations and increases quantum efficiency, especially for LEDs with small dimensions, by minimizing the impact of etching-induced degradation and optimizing the semiconductor material composition.
Implementation Method 1
applying to the sides of the active layer, at the level of the lateral walls of the trench, a chemical treatment capable of etching a first component of the semiconductor alloy selectively over at least another component of the semiconductor alloy
Implementation Method 2
at step b), the trench is formed by a dry etching method
Implementation Method 3
the bandgap width of the semiconductor alloy is a function of the concentration of the first component in the alloy
Data Source
AI summary
A light-emitting diode manufacturing method, including the successive steps of: a) forming an active layer including a stack of multiple quantum wells, each quantum well including a layer made of a semiconductor alloy; b) forming a trench for singularizing the diode, the trench crossing the active layer; and c) applying to the sides of the active layer, at the level of the lateral walls of the trench, a chemical treatment capable of etching a first component of the semiconductor alloy selectively over at least another component of the semiconductor alloy, wherein the bandgap width of the semiconductor alloy is a function of the concentration of the first component in the alloy.