VCSEL Oxide Aperture Etch-Stop Layout for Lower Absorption Loss
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Solution Overview
Problem
Conventional Vertical Cavity Surface Emitting Lasers (VCSELs) with intracavity contacts require extreme tolerances in the etching process and thick epitaxial layers, leading to high absorption losses and reduced efficiency.
Innovation Solution
Incorporating an Al1-xGaxAs layer with 0≤x≤0.05 as both an oxide aperture and etch-stop layer, allowing for precise etching and thin contact layer formation without excessive epitaxial thickness, reducing absorption losses and improving current and optical confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional VCSELs use intracavity contacts with good yield, then manufacturing precision is improved, but absorption losses increase due to thick epitaxial layers
Solution Approach 1:
The patent extracts the etch-stop function from the traditional thick epitaxial layer structure and assigns it to a specific AlAs layer within the semiconductor layer stack. This AlAs layer is selectively removed to create the intracavity contact opening, eliminating the need for extreme etching tolerances while maintaining precise contact formation without requiring excessively thick epitaxial layers that would cause high absorption losses.
Solution Approach 2:
The patent applies local quality by creating a localized AlAs etch-stop layer at the specific position where the intracavity contact is formed. This local modification allows precise control of the etching process only at the contact region, while the rest of the epitaxial layer structure can be optimized for low absorption losses. The etch-stop layer is selectively removed to expose the contact layer, enabling good manufacturing yield without the need for uniformly thick epitaxial layers throughout the entire structure.
2Reliability
If thick epitaxial layers are used to achieve good etching yield, then manufacturing precision is improved, but device efficiency deteriorates due to increased absorption
Solution Approach 1:
The patent extracts the etching yield enhancement function from the uniformly thick epitaxial layer and concentrates it in a localized AlAs etch-stop layer. This allows the overall epitaxial layer to be thinner and more efficient, while the etch-stop layer provides the necessary etching control and yield. The AlAs layer is selectively removed to form the contact opening, achieving high etching yield without requiring the entire epitaxial structure to be thick, thereby maintaining device efficiency.
Solution Approach 2:
The patent changes the composition parameter by introducing an AlAs layer (Al1-xGaxAs with x=0) as an etch-stop layer, which has different etching characteristics compared to the surrounding GaAs-based semiconductor layers. This parameter change enables selective etching with high yield at the contact region while allowing the rest of the epitaxial layer to be optimized for low absorption and high efficiency. The AlAs layer acts as a sacrificial element that is removed after serving its etching control function.
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
Enables high-yield production of VCSELs with reduced absorption losses and improved conductivity, facilitating efficient laser operation without the need for stringent etching tolerances or thick epitaxial layers.
Implementation Method 1
oxidizing the Al1-xGaxAs layer to obtain an oxide aperture layer
Implementation Method 2
etching the layer stack to obtain a first layer sub-stack forming a mesa and a second layer sub-stack adjacent to the mesa
Data Source
AI summary
A method of producing a Vertical Cavity Surface Emitting Laser, including providing a layer stack of semiconductor layers including a first mirror, a second mirror, an active region between the first and second mirrors, an Al1-xGaxAs layer with 0≤x≤0.05, and a contact layer immediately adjacent to the Al1-xGaxAs layer. The method further includes etching the layer stack to obtain a first layer sub-stack forming a mesa and a second layer sub-stack adjacent to the mesa in a stacking direction of the layer stack. Layers of the second layer sub-stack extend beyond layers of the first layer sub-stack in a direction perpendicular to the stacking direction. The Al1-xGaxAs layer is used as an etch-stop layer. The method further includes removing an outer part of the Al1-xGaxAs layer to expose, at least partly, the contact layer, and oxidizing the Al1-xGaxAs layer to obtain an oxide aperture layer.