GaAsP Capped Epitaxial Regrowth for Clean VCSEL DBR Growth
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Solution Overview
Problem
The challenge in fabricating vertical cavity surface emitting lasers (VCSELs) lies in the complexity of epitaxial growth, particularly with the need for precise thickness control and different growth temperatures for InGaAs/GaAsP and AlAs or AlGaAs materials, leading to inefficient processes and compromised growth precision due to cross-contamination and residue issues from native oxide removal.
Innovation Solution
A high precision semiconductor fabrication method involving a GaAsP capping layer for epitaxial regrowth, where the wafer is capped, removed for measurement, and then regrown using in-situ desorption, allowing for separate growth steps in different reactors to avoid contamination and achieve high crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single continuous epitaxial growth process is used for both InGaAs/GaAsP and AlAs/AlGaAs layers, then the fabrication process is simplified, but growth precision is compromised due to different temperature requirements and cross-contamination
Solution Approach 1:
The patent divides the epitaxial growth process into separate stages: first growing the InGaAs/GaAsP layers at lower temperatures, then removing the GaAsP capping layer, and finally growing the AlAs/AlGaAs DBR layers at higher temperatures. This segmentation allows each material system to be grown under its optimal conditions without cross-contamination, resolving the contradiction between process simplicity and growth precision.
2Manufacturing precision
If separate growth processes are used for different materials with different temperature requirements, then growth precision is improved, but fabrication efficiency decreases due to multiple processing steps
Solution Approach 1:
The patent applies preliminary action by growing the InGaAs/GaAsP active region and HCG mirror structures first, then capping with GaAsP before removing the cap and growing the AlAs/AlGaAs DBR layers. This preliminary growth of critical structures allows subsequent regrowth on pre-prepared substrates, improving overall fabrication efficiency while maintaining growth precision through controlled separate processes.
3Productivity
If continuous epitaxial growth is performed, then wafer throughput is maintained, but residue and contamination from native oxide removal compromise crystal quality
Solution Approach 1:
The patent extracts and removes the GaAsP capping layer after the initial growth stage, creating a fresh surface for subsequent AlAs/AlGaAs DBR layer growth. This extraction eliminates contamination from native oxide removal and allows for high-quality crystal growth in the second stage, resolving the contradiction between maintaining throughput and ensuring crystal quality.
4Adaptability or versatility
If the top DBR is replaced with a thin HCG mirror, then epitaxy requirements become more tolerant and device functionality is improved, but the bottom DBR becomes the thickest structure requiring precise growth control
Solution Approach 1:
The patent segments the DBR growth into a separate second growth stage after removing the GaAsP cap layer. This allows the thick AlAs/AlGaAs bottom DBR to be grown under optimized high-temperature conditions with precise thickness control, while the HCG mirror structures were previously grown under different conditions. The segmentation enables independent optimization of each structure's growth parameters.
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 method significantly reduces the epitaxial regrowth time, accelerates the innovation cycle, and achieves excellent laser performance with cost savings by enabling multiple DBR substrate growth in one reactor, while ensuring high wafer throughput and quality.
Implementation Method 1
using in-situ desorption
Implementation Method 2
GaAsP capped material
Data Source
AI summary
A semiconductor device fabrication method in which a growing process is followed by a capping process in which a phosphor containing material cap layer is deposited over a final GaAs based layer. The wafer, containing many such substrates, can be removed from the reaction chamber to continue processing at a later time without creating an oxide layer on the final GaAs based layer. In continuing processing, a decomposition process selectively decomposes the phosphor containing material cap layer, after which a regrowing process is performed to grow additional layers of the device structure. The capping, decomposition and regrowth processes can be repeated multiple times on the semiconductor devices on the wafer during device fabrication.