Buried Heterostructure Laser Mesa Etching Without Sidewall Oxidation
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Solution Overview
Problem
The fabrication of high reliability heterostructure devices like buried heterostructure lasers and semiconductor optical amplifiers is challenging due to spontaneous oxidation of etched walls prior to growth of current blocking layers, leading to etch damage and variations in mesa widths, which affects device performance and reliability.
Innovation Solution
A metal organic chemical vapor deposition (MOCVD) in-situ etching process is used to define the narrow mesa region immediately followed by growth of blocking layers without exposure to oxygen, reducing sidewall oxidation and achieving a smoother etch profile with less than 20% open area and gradual side wall slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching process is used to define mesa structure, then mesa structure can be formed, but spontaneous oxidation of etched walls occurs prior to growth of current blocking layers
Solution Approach 1:
The patent performs the etching process and subsequent current blocking layer growth in-situ within the MOCVD reactor without exposure to ambient air. This inert environment prevents spontaneous oxidation of the etched mesa walls, eliminating the harmful oxidation that would otherwise occur during conventional multi-step processing where the wafer is exposed to air between etching and deposition steps.
Solution Approach 2:
The patent combines the etching process and current blocking layer growth into a single continuous in-situ process within the MOCVD reactor. By merging these two previously separate steps (etching in one tool, then growth in another) into one integrated process, the patent eliminates the air exposure interval that causes oxidation, thereby improving both manufacturing precision and device reliability.
2Ease of manufacture
If conventional etching process is used, then mesa structure can be etched, but etch damage and variations in mesa widths occur
Solution Approach 1:
The patent changes the etching parameters by performing the etch in-situ within the MOCVD reactor using chemically optimized conditions. The etching is achieved through a controlled chemical reaction in the vapor phase, which provides more uniform and damage-free etching compared to conventional plasma or wet etching methods. This parameter change in the etching mechanism eliminates etch damage and width variations while maintaining ease of manufacture.
3Productivity
If standard fabrication process is used, then device can be manufactured, but sidewall oxidation leads to degraded device performance
Solution Approach 1:
The patent maintains continuous processing by performing etching and current blocking layer growth in-situ without breaking the vacuum or exposing the wafer to air. This continuous action eliminates the oxidation that would occur during interruptions in the process, thereby maintaining high device performance while preserving fabrication throughput. The useful action of protecting the mesa walls from oxidation is maintained continuously throughout the process.
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 results in defect-free surfaces, improved reliability, and enhanced performance of heterostructure devices with reduced noise and optimal beam shapes, as evidenced by life test data and SEM images showing smoother structures and increased device efficiency.
Implementation Method 1
growing epitaxial layers of a substrate of first dopant type, an active region and a layer of second dopant type
Implementation Method 2
a narrow mesa having less than 20% open area and a side wall slope of less than 85 degrees, wherein said narrow mesa is etched through the active region and layer of second dopant type using in-situ MOCVD
Implementation Method 3
growing epitaxial layers of a substrate of first dopant type, an active region and a layer of second dopant type
Data Source
AI summary
A heterostructure laser is provided comprising an epitaxially grown substrate of first dopant type, an active region and layer of second dopant type, a narrow mesa having less than 20% open area and a side wall slope of less than 85 degrees, wherein said narrow mesa is etched through the active region and layer of second dopant type using in-situ MOCVD, a plurality of current blocking layers, an overclad layer and a contact layer of second dopant type, and an isolation mesa incorporating the narrow mesa, wherein the isolation mesa is etched through the active region, layer of second dopant type and plurality of current blocking layers and wherein the plurality of current blocking layers is grown without exposure to oxygen.