Semiconductor Filter Layer for Visible Glow Suppression in IR LEDs
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Solution Overview
Problem
Optoelectronic semiconductor devices, such as light-emitting diodes, emit a significant portion of electromagnetic radiation in the visible spectral range, causing an annoying reddish glow, which reduces efficiency and is not effectively filtered by existing technologies.
Innovation Solution
An optoelectronic semiconductor layer sequence is developed with a filter layer having a direct band gap semiconductor material, epitaxially grown to absorb and re-emit electromagnetic radiation of wavelengths smaller than a predetermined cutoff wavelength, reducing high-energy electron-hole pairs and enhancing efficiency by filtering visible radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light-emitting diode emits electromagnetic radiation in the infrared spectral range, then the device can generate useful infrared radiation, but a significant portion of radiation is emitted in the visible spectral range causing an annoying reddish glow and reducing efficiency
Solution Approach 1:
The patent applies this principle by using the filter layer to absorb the harmful visible spectrum radiation (reddish glow) and convert it into useful infrared radiation through photoluminescence. The filter layer material absorbs high-energy visible photons and re-emits them as lower-energy infrared photons, transforming the harmful visible emission into beneficial infrared radiation that matches the desired output spectrum, thereby improving overall efficiency while eliminating the annoying glow
Solution Approach 2:
The patent changes the optical parameters of the semiconductor structure by introducing a filter layer with specific photoluminescence properties. The filter layer has a bandgap energy that corresponds to the visible spectrum absorption edge, allowing it to selectively absorb visible radiation and re-emit infrared radiation. This parameter change in the energy distribution of emitted radiation transforms the spectral composition from harmful visible + infrared to primarily useful infrared
2Object-generated harmful factors
If a filter layer is introduced to absorb visible radiation, then the reddish glow is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the filtering function with the existing semiconductor layer structure by epitaxially growing the filter layer directly onto the active layer in a monolithic integration. The filter layer is combined with cladding layers and other structural elements to form an integrated semiconductor device, eliminating the need for separate filtering components and reducing overall device complexity despite adding functional layers
Solution Approach 2:
The filter layer serves multiple functions simultaneously: it acts as a visible radiation absorber, an infrared radiation emitter, a structural component of the semiconductor device, and a means to improve overall device efficiency. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device 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 filter layer absorbs over 90% of electromagnetic radiation in the visible range, reducing high-energy electron-hole pairs and increasing the efficiency of the optoelectronic semiconductor layer sequence by re-emitting radiation at or near the cutoff wavelength, thereby minimizing unwanted visible emission.
Implementation Method 1
the filter layer absorbs more than 90% of the electromagnetic radiation of wavelengths smaller than the predetermined cutoff wavelength
Implementation Method 2
the electromagnetic radiation absorbed by the filter layer is not entirely converted into heat, but is at least partially re-emitted by the filter layer at or near the cutoff wavelength
Implementation Method 3
the active layer is preferably configured to generate spontaneous emission
Data Source
AI summary
The invention relates to an optoelectronic semiconductor layer sequence comprising:—an active layer for generating radiation, and—at least one filter layer configured to at least partially absorb the electromagnetic radiation generated by the active layer of wavelengths smaller than a predetermined cutoff wavelength. The invention also relates to an optoelectronic semiconductor device.