Semiconductor Laser Wavelength Uniformity via PL Evaluation
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Solution Overview
Problem
Existing methods for manufacturing semiconductor devices, such as those used in optical fiber communication, struggle to sufficiently reduce variations in the difference value between photoluminescence wavelength and oscillating wavelength, leading to suboptimal current-optical output and frequency characteristics.
Innovation Solution
The method involves forming a semiconductor device with a light absorption layer and laser section, where the optical modulator is created first on a flat substrate surface, followed by the formation of a laser section with a diffraction grating and a diffusion constraining layer to stabilize the photoluminescence wavelength, using the same type of dopant for the contact and upper light confinement layers to prevent dopant diffusion, and optimizing the diffraction grating density based on evaluated photoluminescence wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the optical modulator is formed before the laser section using a butt joint method, then the optical modulator can be formed on a flat surface which makes uniform the composition of the light absorption layer and stabilizes the photoluminescence wavelength, but the variation in the difference value between photoluminescence wavelength and oscillating wavelength cannot be reduced sufficiently (only ±2 nm tolerance)
Solution Approach 1:
The optical modulator is formed first on the substrate before forming the laser section. This preliminary formation allows the light absorption layer to be deposited on a flat surface, ensuring uniform composition and stable photoluminescence wavelength before subsequent processing steps
Solution Approach 2:
The invention changes the formation sequence and structural parameters by forming the optical modulator first, then forming the laser section with a diffraction grating in a separate subsequent step, allowing independent optimization of each component's parameters to achieve better wavelength control
2Ease of manufacture
If the laser section is formed after the optical modulator, then the optical modulator benefits from flat surface formation, but the dopant from the contact layer may diffuse into the light absorption layer causing wavelength instability
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the contact layer and the light absorption layer. This barrier layer prevents dopant diffusion from the contact layer into the light absorption layer, thereby stabilizing the photoluminescence wavelength while maintaining the sequential formation process
Solution Approach 2:
The diffusion barrier layer is formed in advance to prevent the harmful dopant diffusion before it can occur. This preliminary protective action stops the dopant from migrating into the light absorption layer during subsequent contact layer formation or device operation
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 effectively reduces variations in the difference value between photoluminescence and oscillating wavelengths, stabilizing the photoluminescence wavelength and oscillating wavelength, thereby enhancing the semiconductor device's performance in terms of current-optical output and frequency characteristics.
Implementation Method 1
forming a diffusion constraining layer that constrains diffusion of a dopant on the upper light confinement layer
Implementation Method 2
forming a laser section having a diffraction grating in a portion of the substrate where the optical modulator is not formed
Implementation Method 3
forming a lower light confinement layer on a substrate, a light absorption layer on the lower light confinement layer and an upper light confinement layer on the light absorption layer
Implementation Method 4
evaluating photoluminescence wavelengths of individual optical modulators of the plurality of optical modulators
Data Source
AI summary
A semiconductor device manufacturing system includes: a PL evaluation apparatus that evaluates wavelengths of photoluminescent light produced by individual optical modulators on a single semiconductor wafer; an electron beam drawing apparatus that draws patterns of diffraction gratings of laser sections that adjoin respective optical modulators on the wafer; and a calculation section that receives the wavelengths of the photoluminescent light from the PL evaluation apparatus, calculates densities of respective diffraction gratings so that differences between the wavelengths of the photoluminescent light and oscillating wavelengths of the laser sections become a constant, and sends the densities calculated to the electron beam drawing apparatus for drawing respective diffraction grating patterns on the respective laser sections.