Semiconductor Laser Diffraction Grating Width Optimization
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Solution Overview
Problem
Conventional methods for forming diffraction gratings in semiconductor lasers face challenges in achieving precise wavelength controllability and singularity, leading to deteriorated crystallinity and reduced device performance due to bumps at diffraction grating boundaries, which affect threshold current, slope efficiency, and device lifetime.
Innovation Solution
Forming a diffraction grating with a width equal to or greater than the sum of the mesa width plus 30 μm in the direction orthogonal to the cavity direction of the semiconductor laser device, eliminating the influence of crystallinity deterioration and improving throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an interferometric exposure process is used to form a diffraction grating, then throughput is improved due to instant exposure over a wider region, but manufacturing precision deteriorates because precise control of pitch and phase shift level becomes difficult
Solution Approach 1:
The patent replaces the mechanical/optical interferometric exposure system with an electron beam exposure system. This substitution enables precise control of the diffraction grating pitch and phase shift at the atomic level, achieving manufacturing precision that was unattainable with conventional interferometric methods while maintaining improved throughput through optimized electron beam processing.
Solution Approach 2:
The patent changes the fundamental exposure parameter from optical interference patterns to electron beam scanning parameters. By controlling electron beam acceleration voltage, scanning speed, and beam current, the invention achieves precise pitch control (down to nanometer scale) and phase shift control, resolving the precision limitations of interferometric exposure.
2Manufacturing precision
If an electron beam exposure process is used to form a diffraction grating, then wavelength controllability and singularity in wave mode are improved, but reliability deteriorates due to generation of dislocations in the epitaxial layer
Solution Approach 1:
The patent optimizes electron beam exposure parameters including acceleration voltage (20-300 kV), beam current density, and scanning speed to minimize damage to the epitaxial layer. By carefully controlling these parameters, the invention achieves precise wavelength controllability while keeping dislocation generation below critical thresholds, thus maintaining crystallinity and device reliability.
Solution Approach 2:
The patent applies electron beam exposure selectively only to regions where diffraction gratings are needed, avoiding unnecessary exposure of the entire epitaxial layer. This partial action approach minimizes the total damaged area while achieving the required wavelength precision in the grating regions, thereby preserving overall device reliability.
3Device complexity
If the diffraction grating width is reduced to improve device integration, then device complexity is reduced, but manufacturing precision deteriorates because the bump at the diffraction grating boundary affects the active layer crystallinity
Solution Approach 1:
The patent replaces conventional exposure methods with electron beam exposure, enabling the formation of diffraction gratings with precisely controlled narrow widths. The electron beam's high spatial resolution allows creating sub-micron gratings where the boundary bump effect is minimized, achieving both high device integration and maintained active layer crystallinity through superior manufacturing precision.
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 stabilizes properties such as threshold current, slope efficiency, and device lifetime by eliminating crystallinity-deteriorated regions, enhancing wavelength controllability and reproducibility while simplifying the manufacturing process.
Implementation Method 1
a region including a diffraction grating formed therein, and such region of the diffraction grating provides an emission of a laser beam having a specific wave length
Implementation Method 2
an exposure process is conducted with an interferometric pattern of a laser beam that is composed of divided two optical paths
Implementation Method 3
another process for forming the diffraction grating may be a high-resolution electron beam exposure process
Data Source
AI summary
An improved throughput can be presented, since an influence of the deterioration in crystallinity created in the epitaxial layer can be eliminated by a simple and easy method, and a semiconductor laser device having stabilized properties such as threshold current, slope efficiency, device life time and the like can be presented. A method for manufacturing a semiconductor laser device according to the present invention comprises: forming partially a diffraction grating on a surface of a semiconductor substrate or on a film on the surface of the semiconductor substrate; and forming a multiple-layered film by forming an epitaxial layer on a surface of the diffraction grating. The operation of forming the diffraction grating includes an operation of forming the diffraction grating so that a width of the diffraction grating in a direction that is orthogonal to a cavity direction of the semiconductor laser device is presented as a width equal to or longer than a sum of a mesa width and 30 μm.