Off-Axis GaAs VCSEL Structure for Strain Defect Suppression
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Solution Overview
Problem
Existing vertical cavity surface-emitting lasers face challenges in maintaining high photoluminescence intensity and laser characteristics due to strain-induced defects and As-loss defects, which degrade performance.
Innovation Solution
A vertical cavity surface-emitting laser design with a GaAs substrate having an off angle of 6° or more, incorporating an active layer of InxAlyGa1-x-yAs with a strain of 0.5% to 1.4%, and a current confinement layer with controlled carbon concentration, reduces strain-related defects and As-loss, enhancing photoluminescence intensity and laser performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the active layer has a high In composition to achieve desired wavelength emission, then the laser wavelength can be tuned to 830 nm to 910 nm, but strain-induced defects and As-loss defects increase, degrading photoluminescence intensity
Solution Approach 1:
The patent changes the physical parameter of the substrate orientation from conventional (001) to off-axis orientations such as (100) with 6-15 degrees off-angle or (110) with 6-15 degrees off-angle. This parameter change in substrate orientation fundamentally alters the growth conditions and strain distribution in the InxAlyGa1-x-yAs active layer, enabling high photoluminescence intensity while maintaining reliable laser characteristics by reducing defect formation.
2Speed
If the strain in the active layer is increased to improve laser performance, then the relaxation oscillation frequency can be enhanced, but strain-induced defects increase, reducing photoluminescence intensity
Solution Approach 1:
The patent optimizes the composition parameters of the InxAlyGa1-x-yAs active layer and adjusts the strain within the range of 0.1% to 1.5% by controlling the thickness and composition of quantum well layers. Simultaneously, the off-axis substrate orientation parameter is utilized to manage strain distribution, achieving enhanced relaxation oscillation frequency while preventing excessive strain-induced defects that would reduce photoluminescence intensity.
3Ease of manufacture
If conventional (001) oriented GaAs substrate is used, then the manufacturing process is simple and well-established, but As-loss defects occur during growth, degrading laser characteristics
Solution Approach 1:
The patent changes the substrate orientation parameter from conventional (001) to off-axis orientations including (100) with 6-15 degrees off-angle or (110) with 6-15 degrees off-angle. This parameter change suppresses As-loss defects during molecular beam epitaxial growth while maintaining manufacturing feasibility through established off-cut substrate preparation techniques, thereby improving laser characteristics without significantly complicating the manufacturing process.
4Reliability
If high carbon concentration is used to fill As-loss defects, then the laser characteristics can be maintained, but the surface roughness increases and photoluminescence intensity decreases
Solution Approach 1:
The patent changes the substrate orientation parameter to off-axis orientations of (100) with 6-15 degrees off-angle or (110) with 6-15 degrees off-angle, which fundamentally suppresses the formation of As-loss defects during growth. This parameter change eliminates the need to use high carbon concentration for defect filling, thereby maintaining reliable laser characteristics while avoiding the negative effects of increased surface roughness and reduced photoluminescence intensity associated with carbon doping.
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
The design achieves high photoluminescence intensity, reduced surface roughness, and improved relaxation oscillation frequency, while maintaining excellent laser characteristics without the need for high carbon concentrations to fill defects.
Implementation Method 1
first distributed Bragg reflector and a second distributed Bragg reflector
Data Source
AI summary
A vertical cavity surface-emitting laser configured to emit laser light having a wavelength of 830 nm to 910 nm includes a substrate having a main surface including GaAs, a first distributed Bragg reflector, an active layer, and a second distributed Bragg reflector. The substrate, the first distributed Bragg reflector, the active layer, and the second distributed Bragg reflector are arranged in a first axis direction intersecting the main surface. The main surface has an off angle of 6° or more with respect to a (100) plane. The active layer includes InxAlyGa1-x-yAs (0<x<1, 0≤y<1). The active layer has a strain. An absolute value of the strain is 0.5% to 1.4%.