Gap Distributed Bragg Reflectors for High Reflectivity
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Solution Overview
Problem
Conventional semiconductor light emitting devices with distributed Bragg reflectors (DBRs) face challenges in achieving high reflectivity with a low number of mirror pairs, leading to potential defects and structural issues due to low refractive index differences between alternating layers, especially in nitride-containing materials.
Innovation Solution
The formation of gap DBRs by epitaxially growing alternating reflective and interstitial layers, where the interstitial layers are selectively etched to create air gaps between the reflective layers, increasing the refractive index difference and allowing for higher reflectivity with fewer mirror pairs, using materials like GaN and AlGaN with differential etch rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional DBRs with nitride-containing materials are used, then the device structure is simple and manufacturing is easier, but the refractive index difference between alternating layers is low, resulting in insufficient reflectivity with a high number of mirror pairs required
Solution Approach 1:
The patent changes the refractive index parameter by replacing conventional nitride-containing materials with a combination of oxide semiconductor layers (first material) and semiconductor layers (second material). This material substitution fundamentally alters the optical parameters, creating a large refractive index difference that enables high reflectivity with fewer mirror pairs
Solution Approach 2:
The patent employs composite material structures by alternating oxide semiconductor layers with semiconductor layers. This composite approach combines materials with complementary properties - the oxide semiconductor provides high refractive index contrast while the semiconductor layer provides appropriate optical and electrical characteristics, achieving superior reflectivity performance
2Reliability
If a high number of mirror pairs are used to achieve high reflectivity, then the reflectivity increases, but the device complexity increases and structural defects become more likely
Solution Approach 1:
By fundamentally changing the material parameters (refractive index) through oxide semiconductor integration, the patent achieves high reflectivity with a reduced number of mirror pairs, directly lowering device complexity and the associated risk of structural defects
Solution Approach 2:
The patent extracts and removes the unnecessary complexity by using fewer mirror pairs. The high refractive index contrast provided by oxide semiconductor layers eliminates the need for numerous alternating layers, thereby reducing structural complexity and potential defect sites
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 achieves reflectivity greater than 99% with fewer than 20 reflector pairs, reducing the risk of defects and structural issues, and enables the use of the devices in applications such as VCSEL structures with a lower lasing threshold.
Implementation Method 1
The interstitial layers are exposed to an etchant through the vias and are etched
Implementation Method 2
A light emitting layer, one or more reflective layers, and one or more interstitial layers are epitaxially grown
Implementation Method 3
increasing the refractive index difference and allowing for higher reflectivity with fewer mirror pairs
Data Source
AI summary
A device includes one or more reflector components. Each reflector component comprises layer pairs of epitaxially grown reflective layers and layers of a non-epitaxial material, such as air. Vias extend through at least some of the layers of the reflector components. The device may include a light emitting layer.