VCSEL Mesa Taper and Reflectance Feedback for Oxidation Control
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Solution Overview
Problem
Existing methods for manufacturing vertical cavity surface emitting lasers face challenges in achieving uniform laser emission properties and high yield due to issues with selective oxidation layer size control, leading to increased costs and reduced efficiency, particularly with methods that require complex patterning or close microscope observation, which can distort moisture vapor distribution and optical elements.
Innovation Solution
The solution involves forming a vertical cavity surface emitting laser element with a mesa structure having different taper angles for the upper and lower parts, utilizing a detectable step portion to accurately measure the selective oxidation layer position and thickness, and applying an insulating film and thicker upper electrode to ensure uniform oxidation and prevent electrode disconnection, while using plasma etching and controlled oxidation processes to maintain precise layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a monitored oxidation pattern is used to indirectly monitor the degree of oxidation, then the oxidation rate can be monitored, but the area for mounting the laser element is limited and cost increases
Solution Approach 1:
The patent extracts the monitoring function from a separate pattern structure and integrates it into the resonator structure itself. The resonator pattern serves dual purposes: as the functional laser element and as the monitoring pattern, eliminating the need for additional blank patterns around monitored oxidation patterns.
Solution Approach 2:
The resonator pattern is given multiple functions: it serves as both the operational laser resonator structure and the monitoring pattern for oxidation rate measurement. This multi-functionality eliminates the need for separate monitoring patterns and increases the usable mounting area.
2Measurement precision
If a microscope is used to observe the degree of oxidation in real time, then the oxidation process can be controlled, but the distance between the observation port and semiconductor member must be shortened, causing moisture vapor distribution to scatter and oxidation to become non-uniform
Solution Approach 1:
The patent implements feedback control by measuring the reflectance of the resonator pattern during oxidation and using this information to control the oxidation process. This eliminates the need for microscope observation and allows maintaining optimal oxidation conditions without scattering moisture vapor distribution.
Solution Approach 2:
The patent replaces the mechanical microscope observation system with an optical reflectance measurement system. This substitution allows monitoring from a distance without physically disturbing the moisture vapor distribution around the semiconductor member.
3Extent of automation
If the distance between the observation port and semiconductor member is shortened for microscope focus, then real-time observation is possible, but optical elements may be deformed by heat and focus deviates, degrading measurement accuracy
Solution Approach 1:
The patent replaces the microscope-based mechanical observation system with a reflectance-based optical measurement system that operates from a distance, eliminating heat-induced deformation and focus deviation problems.
Solution Approach 2:
The patent uses reflectance measurement as an intermediary method to monitor oxidation without direct visual observation. This intermediary approach allows measurement without physical proximity, avoiding heat-related distortion of optical elements.
4Reliability
If the unoxidized region size deviates from the optimum value, then laser oscillation characteristics deviate, but controlling the oxidation process precisely is difficult
Solution Approach 1:
The patent uses feedback control where the reflectance of the resonator pattern is measured during oxidation and this information is used to control the oxidation process, ensuring the unoxidized region achieves the optimal size for proper laser oscillation characteristics.
Solution Approach 2:
The patent monitors and controls oxidation by measuring reflectance, a physical parameter that changes during the oxidation process. This allows precise control of the oxidation degree to achieve the optimal unoxidized region size.
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 enables the production of vertical cavity surface emitting lasers with uniform laser emission properties at a lower cost, improving yield by accurately controlling the oxidation process and preventing electrode disconnection, thus enhancing the manufacturing efficiency and accuracy of the current blocking layer.
Implementation Method 1
oxidizing it from an outer peripheral portion on a side surface of the mesa structure, made of a p-AlAs or AlGaAs layer, to the center of the mesa structure, and forming a selective oxidation layer made of a region of the oxidized AlO and an unoxidized region
Implementation Method 2
a mesa structure formed by removing parts of the semiconductor layer by plasma etching or the like
Data Source
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AI summary
A disclosed vertical cavity surface emitting laser element includes a substrate, a laminated body sandwiching a semiconductor active layer with an upper reflecting mirror and a lower reflecting mirror, a lower electrode, and an upper electrode. The laser element emits laser light in a direction perpendicular to the surface of the substrate when an electric current is supplied between the upper electrode and the lower electrode. The laser element further includes a selective oxidation layer in the upper reflecting mirror having a current blocking structure made of an oxidized region and an unoxidized region, and a detectable portion formed on a side surface of a mesa structure shaped by the upper reflecting mirror including the selective oxidation layer and the active layer, thereby enabling detecting the position of the selective oxidation layer from a top of the laminated body in a depth direction of the laminated body.