LED Wafer Spectrum Tuning with Photo- and Electroluminescent Wells
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Solution Overview
Problem
Existing LED devices have a fixed emission spectrum after epitaxial growth, making it difficult and costly to produce LEDs with different spectral characteristics on the same wafer, which is a limitation in applications like display and camera flash modules where color uniformity is crucial.
Innovation Solution
The development of LED devices with a combination of photoluminescent and electroluminescent quantum wells, allowing for adjustable emission spectra through post-growth wafer processing, including varying the optical path length and using wavelength-selective reflector coatings, enables the production of LEDs with different emission spectra on the same wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different spectral characteristics are desired, a different wafer must be grown, then spectral characteristics can be changed, but manufacturing complexity and cost increase
Solution Approach 1:
The wafer is divided into multiple regions with different emission spectra by selectively removing photoluminescent quantum wells in different areas. This segmentation allows each region to have tailored spectral characteristics while maintaining a single unified wafer structure, avoiding the need to grow multiple separate wafers.
Solution Approach 2:
The photoluminescent quantum wells are pre-formed throughout the entire wafer during epitaxial growth, but their functionality is selectively activated or deactivated in different regions through subsequent processing steps. This preliminary action enables spectrum adjustment without requiring separate wafer growth for each spectral characteristic.
2Productivity
If LEDs with different emission spectra are fabricated in close proximity on the same wafer, then manufacturing efficiency improves, but color uniformity control becomes more difficult
Solution Approach 1:
Different regions of the wafer are given different local qualities by selectively removing photoluminescent quantum wells in specific areas. This allows each region to have the appropriate spectral characteristics for its intended application while maintaining precise control over color uniformity within each region through localized processing.
3Adaptability or versatility
If multiple epitaxial wafers are used to produce LEDs with different spectral characteristics, then emission spectrum variety improves, but manufacturing cost increases
Solution Approach 1:
Multiple spectral characteristics that would traditionally require separate epitaxial wafers are merged into a single wafer by forming photoluminescent quantum wells throughout the entire structure and then selectively removing them in different regions. This combining approach reduces manufacturing cost by eliminating the need to grow and process multiple separate wafers.
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 allows for the fabrication of LEDs with adjustable emission spectra on the same wafer, reducing the need for multiple epitaxial wafers and minimizing color variations, thereby simplifying the manufacturing process and improving color uniformity in applications.
Implementation Method 1
the first mesa and the second mesa comprising a photoluminescent quantum well
Implementation Method 2
an electroluminescent quantum well on the n-type layer
Data Source
AI summary
Described are light emitting diode (LED) devices including a combination of electroluminescent and photo-luminescent active regions in the same wafer to provide LEDs with emission spectra that are adjustable after epitaxial growth. The LED device includes a multilayer anode contact comprising a reflecting metal and at least one transparent conducting oxide layer in between the metal and the p-type layer surface. The thickness of the transparent conducting oxide layer may vary for LEDs fabricated with different emission spectra.