Nitride Semiconductor Facet Coating for Reflectance and COD
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Solution Overview
Problem
Nitride semiconductor laser devices face challenges in achieving high reflectance at the light-emitting facet while maintaining a high Catastrophic Optical Damage (COD) level, as conventional AR coating films do not sufficiently improve reflectance and often result in low COD levels.
Innovation Solution
A nitride semiconductor light-emitting device with a coating film of aluminum oxynitride or aluminum nitride and a reflectance control film of oxide films, specifically a stack of aluminum oxide and silicon oxide, is used to enhance reflectance and COD levels, with oxygen content between 0 to 35 atomic percent, and additional layers on the light-reflecting facet to achieve desired reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single layer of silicon oxide, aluminum oxide, titanium oxide, or zinc oxide is formed as an AR coating film on the light-emitting facet, then the reflectance is reduced, but the improvement in reflectance control is insufficient
Solution Approach 1:
The coating film is divided into multiple functional layers: a first coating film (Aluminum Oxynitride or Aluminum Nitride) directly contacting the light-emitting facet, and a second coating film (oxide film with specific refractive index) formed on the first coating film. This segmentation allows each layer to perform its specific function - the first layer provides strong bonding and reduced nonradiative centers, while the second layer provides precise reflectance control through its optical properties.
Solution Approach 2:
The patent uses composite material structures combining different materials with complementary properties. The first coating film uses Aluminum Oxynitride or Aluminum Nitride which have high bonding strength to the nitride semiconductor facet. The second coating film uses oxide films with specifically controlled refractive indices (1.43-2.0) to achieve desired reflectance. This composite approach allows simultaneous optimization of both bonding/COD level and reflectance control.
2Power
If the reflectance at the light-emitting facet is increased to lower mirror loss, then the threshold value is reduced, but the COD level decreases due to increased optical density
Solution Approach 1:
The first coating film (Aluminum Oxynitride or Aluminum Nitride) acts as an intermediary layer between the nitride semiconductor light-emitting facet and the second coating film. This intermediary provides strong chemical bonding that reduces nonradiative centers and enhances the COD level, while allowing the second coating film to control reflectance independently. The intermediary layer decouples the relationship between reflectance and COD level, enabling simultaneous optimization of both parameters.
Solution Approach 2:
The patent adds a temporal/dimensional sequence to the coating structure by forming the first coating film before the second coating film. This sequential formation allows the first layer to establish strong bonding and high COD level first, then the second layer is added to control reflectance. This dimensional approach (adding layers in sequence) allows independent optimization of COD level and reflectance control without trade-offs.
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 solution achieves higher reflectance at the light-emitting facet while maintaining a high COD level, improving the device's performance and longevity by reducing nonradiative centers and enhancing contact between the facet and the coating film.
Implementation Method 1
it has been found that when a coating film formed of an aluminum oxynitride film or an aluminum nitride film is formed on a light-emitting facet of a cavity, a bond between the nitride semiconductor light-emitting facet and the coating film is enhanced, and nonradiative centers are reduced
Implementation Method 2
an AR (Anti-Reflectance) coating film for attaining the reflectance of approximately 10% at the facet of the cavity with respect to the laser beams may be formed on a light-emitting facet of the cavity
Data Source
AI summary
A nitride semiconductor light-emitting device including a coating film and a reflectance control film successively formed on a light-emitting portion, in which the light-emitting portion is formed of a nitride semiconductor, the coating film is formed of an aluminum oxynitride film or an aluminum nitride film, and the reflectance control film is formed of an oxide film, as well as a method of manufacturing the nitride semiconductor light-emitting device are provided.