Quantum Cascade Laser Substrate Replacement for Terahertz Extraction
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Solution Overview
Problem
Quantum cascade laser beam sources face challenges in achieving high terahertz wave extraction efficiency due to absorption by Fe-doped InP substrates, while also requiring sufficient strength to withstand external forces during manufacturing.
Innovation Solution
A method involving the sequential stacking of semiconductor layers on an InP substrate, followed by etching to form specific excavated portions and electrodes, and replacing the InP substrate with a silicon substrate to reduce absorption and enhance structural strength, including the formation of circumferential edge portions for improved bonding and electrode configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an Fe-doped (semi-insulating) InP single-crystal substrate is used, then the semiconductor element has sufficient strength to withstand external forces, but the substrate absorbs terahertz waves and reduces output
Solution Approach 1:
The patent removes the Fe-doped InP single-crystal substrate from the semiconductor element structure. By extracting this substrate that causes terahertz wave absorption, the harmful effect is eliminated while the semiconductor element is reconfigured to function without it, achieving high extraction efficiency of terahertz waves.
Solution Approach 2:
The patent introduces a support substrate as an intermediary component during the manufacturing process. This support substrate provides mechanical strength and stability during fabrication, allowing the semiconductor element to be formed and then subsequently removed, thereby achieving both structural integrity during manufacturing and minimal terahertz absorption in the final product.
2Object-generated harmful factors
If the Fe-doped InP substrate is removed, then terahertz wave extraction efficiency is improved, but the semiconductor element becomes too thin and weak to withstand external forces
Solution Approach 1:
The support substrate serves as a temporary intermediary that provides mechanical strength during the manufacturing process. It allows the thin semiconductor element (without the Fe-doped InP substrate) to be formed and handled, and is removed after the silicon substrate is bonded, thus enabling both high terahertz extraction efficiency and sufficient structural strength.
Solution Approach 2:
The patent creates a composite structure by bonding a silicon substrate to the semiconductor element. The silicon substrate provides mechanical strength and stability, while the semiconductor element maintains its thin configuration for high terahertz wave extraction efficiency, achieving a combination of properties from different materials.
3Object-generated harmful factors
If a silicon substrate is bonded to the semiconductor element, then terahertz wave extraction efficiency is improved, but manufacturing complexity increases due to additional bonding and peeling steps
Solution Approach 1:
The patent performs preliminary bonding of the silicon substrate to the semiconductor element while the support substrate is still in place. This preliminary action allows the thin semiconductor element to be stabilized before the support substrate is removed, simplifying the overall manufacturing process by preventing potential damage during subsequent handling.
Solution Approach 2:
The manufacturing process is segmented into distinct stages: bonding the silicon substrate while the support substrate is present, then removing the support substrate. This segmentation allows each step to be optimized independently, managing the complexity of the overall process while achieving the desired outcome of high terahertz extraction efficiency.
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 enhances terahertz wave extraction efficiency and provides sufficient strength to the semiconductor element, allowing for effective operation and thermal management, while preventing cracking or disconnection during bonding and assembly.
Implementation Method 1
there is a large absorption coefficient in a terahertz frequency band in Group III-V compound semiconductors such as InP and GaAs. Accordingly, in such a DFG-QCL beam source, there is a problem in that the Fe-doped (semi-insulating) InP single-crystal substrate can easily absorb terahertz waves
Implementation Method 2
a step of preparing a semiconductor stacked body in which a lower contact layer, a lower clad layer, a lower guide layer, an activation layer, and an upper guide layer are sequentially stacked on an indium phosphide substrate
Implementation Method 3
a step of partially performing etching on the semiconductor stacked body to form a pair of first excavated portions in which the lower clad layer is exposed by the etching
Data Source
AI summary
A method of manufacturing a quantum cascade laser beam source (1) includes: preparing a semiconductor stacked body (20); forming a pair of first excavated portions (41 and 42) and a ridge portion which is interposed between the pair of first excavated portions (41 and 42); forming channel structures (51 and 52) and circumferential edge portions (61 and 62) which are formed to interpose the channel structures (51 and 52) between the ridge portion (30) and the circumferential edge portion; forming an electrode pattern (81) in contact with a first area (29a) and forming an electrode pattern (82) in contact with a second area (22a); fixing a crystal growth surface side to a support substrate (91); removing an Fe-doped (semi-insulating) InP single-crystal substrate (21); fixing a Si substrate (93); and peeling the support substrate (91).