Laser Diode Fabrication via Self-Aligned Etching
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Solution Overview
Problem
Conventional methods for fabricating semiconductor laser diodes using self-alignment face challenges such as low precision and insufficient contact area between the upper contact layer and the p-type upper electrode, leading to increased operating voltage and leakage current due to the limitations of the liftoff method and etchback process.
Innovation Solution
A method involving the sequential formation of layers including a sacrificial layer and a buried layer, where the sacrificial layer is selectively etched using a buffered oxide etchant or HF solution, allowing for precise removal and enhancing the precision and reliability of the fabrication process, thereby stabilizing the ridge waveguide structure and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography using a mask is used to form a contact hole, then the contact hole can be formed in the buried layer, but the manufacturing precision is low and the contact area between upper contact layer and p-type upper electrode is insufficient
Solution Approach 1:
The patent forms a ridge waveguide structure before forming the contact hole, using the ridge structure as a preliminary feature that guides subsequent self-aligned etching. This preliminary structure enables precise contact hole formation without requiring complex mask alignment, as the etch process naturally follows the ridge geometry to create the contact hole at the correct position with adequate contact area.
2Manufacturing precision
If liftoff method using selective solution is used to form self-aligned contact hole, then self-alignment is achieved, but the buried layer thickness must be limited below a predetermined value and only restricted range of materials can be used
Solution Approach 1:
The patent replaces the chemical liftoff method with a physical self-aligned etching process. Instead of using selective chemical solutions that dissolve the buried layer, the invention uses controlled etching that follows the ridge waveguide structure to automatically position the contact hole. This substitution eliminates material compatibility constraints and thickness limitations while maintaining self-alignment precision.
3Manufacturing precision
If etchback process is used to form contact hole by etching photoresist on ridge, then contact hole can be formed, but etch stop point cannot be grasped and outer portion of contact hole overlaps outer portion of top surface of upper contact layer causing elevated operating voltage
Solution Approach 1:
The patent employs a self-aligned etching process where the ridge waveguide structure itself serves as the alignment reference for contact hole formation. The etch process automatically stops at the appropriate depth by following the ridge geometry, eliminating the need for external etch stop layers or complex monitoring. This self-service mechanism ensures the contact hole is positioned precisely without overlapping the upper contact layer edges, maintaining stable operating voltage.
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 method improves the precision and reliability of the fabrication process, reduces leakage current, and allows for effective heat dissipation by increasing the contact area between the upper contact layer and the p-type upper electrode, resulting in a more efficient and stable semiconductor laser diode.
Implementation Method 1
the sacrificial layer is selectively etched using a buffered oxide etchant or HF solution
Data Source
AI summary
Provided is a method of fabricating a laser diode. Embodiments of the method include sequentially forming at least a lower clad layer, a resonance layer, an upper clad layer, an upper contact layer, an upper electrode layer, and a sacrificial layer on a substrate; forming a ridge portion by etching the sacrificial layer, the upper electrode layer, the upper contact layer, and a predetermined depth of the upper clad layer; exposing both top surfaces of the upper contact layer and both bottom surfaces of the sacrificial layer corresponding thereto by etching portions of the upper electrode layer, which are exposed on both sides of the ridge portion; forming a buried layer having an opening that exposes at least a portion of the bottom surface of the sacrificial layer, the buried layer formed on the surface of the ridge portion and the top surface of the upper clad layer that extends from the ridge portion; and removing the sacrificial layer and a portion of the buried layer disposed thereon by supplying an etchant through the opening.