Monolithic Multi-Quantum Well LED for White Light
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Solution Overview
Problem
Existing methods for fabricating white light emitting GaN-based LEDs are complex, costly, and suffer from poor reliability, requiring expensive post-processing and phosphor-based wavelength converters, which lead to inefficient power utilization and spectral shifts when viewed at different angles.
Innovation Solution
A monolithic multi-bandgap, multi-quantum well (MQW) structure is employed, comprising nitride-based III-V compound semiconductors with specifically designed quantum wells and barriers to emit light across multiple wavelength bands, allowing for the adjustment of light intensity to produce white light or other preselected colors without the need for phosphor converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphor-based wavelength converters are used to convert UV or blue light to white light, then white light emission is achieved, but power utilization efficiency decreases and spectral shifts occur when viewed at different angles
Solution Approach 1:
The active region is segmented into multiple quantum well structures, each emitting at different wavelengths (blue, green, red). This segmentation eliminates the need for phosphor conversion, directly generating white light with superior power efficiency by converting electrical energy directly to multiple wavelengths simultaneously through electroluminescence in each quantum well segment
Solution Approach 2:
The invention uses composite quantum well structures with different bandgap materials (InGaN for blue, AlInGaN for green, AlGaInP for red) stacked together. This composite approach enables direct multi-wavelength emission without phosphor converters, achieving both white light emission and high power utilization efficiency simultaneously
2Illumination intensity
If phosphor-based wavelength converters are used to convert UV or blue light to white light, then white light emission is achieved, but device reliability decreases due to short lifetime of phosphor materials
Solution Approach 1:
The invention extracts and eliminates the phosphor-based wavelength conversion component from the system entirely. By using multiple quantum well active regions that directly emit different wavelengths, the patent removes the reliability-limiting phosphor materials while maintaining white light emission capability through direct electroluminescence from semiconductor quantum wells
Solution Approach 2:
The invention changes the fundamental emission mechanism parameter from photoluminescence (phosphor-based) to electroluminescence (direct LED emission). This parameter change replaces short-lifetime phosphor materials with stable semiconductor quantum wells that have proven long operational lifetimes, thereby improving device reliability while achieving white light emission
3Illumination intensity
If multiple separate LEDs with individual current supplies are combined to produce white light, then white light emission is achieved, but device complexity and package size increase
Solution Approach 1:
The invention merges multiple separate LED chips (blue, green, red) into a single integrated quantum well structure on one substrate. All quantum well regions share common current supply paths and are controlled by unified driving circuitry, eliminating the need for separate current supplies and complex synchronization circuits while achieving simultaneous multi-wavelength emission for white light
4Reliability
If wafer bonding and post processing are used to fabricate white light LEDs, then device performance is improved, but manufacturing cost and processing complexity increase
Solution Approach 1:
The invention performs preliminary integration by forming all quantum well active regions (blue, green, red) directly on a single substrate during the initial epitaxial growth process. This preliminary action eliminates the need for subsequent expensive wafer bonding and post-processing steps, achieving complete device integration in one manufacturing pass and reducing both cost and 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
This approach simplifies processing, reduces manufacturing costs, enhances reliability, improves power efficiency, and minimizes spectral shifts, enabling the production of white light emitting LEDs with superior performance and reduced complexity.
Implementation Method 1
a multi-bandgap, multi-quantum well (MQW) active light emitting region which emits light at at least two spaced-apart wavelength bands or regions ranging from UV to red regions
Data Source
AI summary
A monolithic, multi-color semiconductor light emitting diode (LED) is formed with a multi-bandgap, multi-quantum well (MQW) active light emitting region which emits light at spaced-apart wavelength bands or regions ranging from UV to red. The MQW active light emitting region comprises a MQW layer stack including n quantum barriers which space apart n−1 quantum wells. Embodiments include those wherein the MQW layer stack includes quantum wells of at least two different bandgaps for emitting light of two different wavelengths, e.g., in the blue or green regions and in at least one other region, and the intensities of the emissions are adjusted to provide a preselected color of combined light emission, preferably white light.