Thin AlGaAs Current Spreading Layer for LED Optical Absorption
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Solution Overview
Problem
Conventional light-emitting diode chips with thick current spreading layers suffer from significant optical absorption and increased moisture sensitivity, particularly when the emitted radiation is of short wavelength or the aluminum content is low.
Innovation Solution
A light-emitting diode chip design featuring a current spreading layer less than 500 nm thick, composed of p-doped Al x Ga 1-x As with a high aluminum content, positioned between the carrier and the p-type semiconductor region, which reduces optical absorption and moisture sensitivity by being better protected from oxidation and environmental influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick current spreading layer is used to achieve uniform current flow, then electrical conductivity is improved, but optical absorption increases
Solution Approach 1:
The patent changes the thickness parameter of the current spreading layer from conventional thick (1-10 μm) to thin (10-500 nm), and adjusts the aluminum content parameter (x) to range from 0.5 to 1.0. This parameter optimization achieves both uniform current distribution and low optical absorption, resolving the technical contradiction between electrical conductivity and optical transmission.
2Loss of energy
If the aluminum content in the current spreading layer is increased to reduce optical absorption, then optical transmission is improved, but sensitivity to moisture increases
Solution Approach 1:
The patent employs a thin film current spreading layer (10-500 nm) made of AlGaAs with high aluminum content. The thin film structure reduces the volume susceptible to moisture while maintaining the optical transmission benefits of high aluminum content. This resolves the contradiction between optical absorption reduction and moisture sensitivity.
3Reliability
If a thick current spreading layer is used to ensure low electrical resistance, then electrical conductivity is improved, but the chip's sensitivity to oxidation and moisture increases
Solution Approach 1:
The patent optimizes the thickness parameter to 10-500 nm and aluminum content to 0.5≤x≤1.0, achieving sufficient electrical conductivity with minimal material volume. The reduced volume inherently lowers sensitivity to oxidation and moisture while maintaining the necessary electrical performance through high aluminum content and appropriate doping.
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 thin current spreading layer achieves low optical absorption and reduced sensitivity to moisture, enhancing the stability and efficiency of the light-emitting diode chip while maintaining effective current distribution.
Implementation Method 1
a current spreading layer less than 500 nm thick, which consists of one or more p-doped Al x Ga 1-x As layer(s) with 0.5≤x≤1.0 and a thickness of less than 500 nm
Implementation Method 2
a not inconsiderable proportion of the emitted radiation is also absorbed. The absorption of a thick current spreading layer is not negligible in particular when the emitted radiation is of short wavelength
Implementation Method 3
a comparatively thick current spreading layer made of a semiconductor material with good electrical conductivity is generally arranged between the electrical contact and the light-emitting semiconductor layer sequence in order to achieve the most uniform possible current flow through the active layer
Data Source
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Figure 3~4
Figure 5
AI summary
A light-emitting diode (LED) chip is described, comprising a semiconductor layer sequence (5) which has a phosphide compound semiconductor material, wherein the semiconductor layer sequence (5) includes a p-type semiconductor region (2), an n-type semiconductor region (4), and an active layer (3) arranged between the p-type semiconductor region (2) and the n-type semiconductor region (4) for the emission of electromagnetic radiation, wherein the n-type semiconductor region (4) faces a radiation emission surface (6) of the LED chip, and the p-type semiconductor region (2) faces a support (7) of the LED chip.Between the support and the p-type semiconductor region (2) a current-expansion layer (1) less than 500 nm thick is arranged, which has one or more p-doped AlxGa1-xAs layer(s) with 0.5 < x ≤ 1, and wherein at least one layer of InxGayAl1-x-yAs with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and x + y ≤ 1 is adjacent to the current-expansion layer (1), which has a smaller band gap and a lower dopant concentration than the current-expansion layer (1).