Nitride Semiconductor Laser P-Type Cladding Strain
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Solution Overview
Problem
Nitride semiconductor lasers face challenges in reducing drive voltage while maintaining optical confinement, with existing technologies experiencing degradation in electrical characteristics and refractive index profiles.
Innovation Solution
A nitride semiconductor laser with a p-type cladding region comprising a first InAlGaN layer and a second p-type Group III nitride semiconductor layer, where the second layer has lower resistivity and different material composition, providing built-in anisotropic strain to enhance optical confinement and reduce drive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer p-type cladding region is used, then the device structure is simple, but the optical confinement is insufficient and drive voltage is high
Solution Approach 1:
The p-type cladding region is divided into two distinct layers: a first p-type Group III nitride semiconductor layer and a second p-type Group III nitride semiconductor layer. This segmentation allows each layer to contribute differently to optical confinement and electrical conduction, resolving the contradiction between structural simplicity and optical confinement performance.
Solution Approach 2:
The invention uses composite material structure with two different p-type Group III nitride semiconductor layers having different materials, resistivities, and bandgap energies. This composite approach enables simultaneous optimization of optical confinement and electrical conduction properties that cannot be achieved with a single material layer.
2Power
If the resistivity of the p-type cladding layer is reduced to lower drive voltage, then electrical conduction improves, but optical confinement degrades
Solution Approach 1:
The first p-type layer is designed with higher resistivity and larger bandgap energy to provide strong optical confinement, while the second p-type layer is designed with lower resistivity to provide excellent electrical conduction and low drive voltage. This local quality differentiation resolves the contradiction between electrical conduction and optical confinement.
Solution Approach 2:
The invention adds a new dimension to the cladding region design by introducing a second layer with different material composition and electrical properties. This dimensional expansion (from single-layer to multi-layer structure) provides additional degrees of freedom to simultaneously optimize both electrical conduction and optical confinement.
3Reliability
If compositionally-graded profile is used in p-type cladding layer, then optical confinement is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of using a compositionally-graded profile within a single layer, the invention segments the cladding region into two distinct layers with abrupt interfaces. This segmentation simplifies the epitaxial growth process by eliminating the need for complex compositional grading while maintaining effective optical confinement through the discontinuous material structure.
Solution Approach 2:
Rather than achieving optical confinement through gradual compositional changes (graded profile), the invention inverts the approach by using abrupt material transitions between two discrete layers. This inverted strategy achieves similar or superior optical confinement with simplified manufacturing.
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 solution effectively reduces the drive voltage while maintaining excellent optical confinement, achieved through the use of a double-layered p-type cladding region with specific resistivity and bandgap energy profiles, leading to improved electrical conduction and reduced absorption losses.
Implementation Method 1
the InAlGaN layer includes built-in anisotropic strain; holes in this InAlGaN layer have a smaller effective mass than those in InAlGaN grown on a c-plane
Implementation Method 2
the p-type cladding region has excellent optical confinement; the refractive index of the MgZnO layer closer to the active layer is smaller than that of the MgZnO layer farther from the active layer
Data Source
AI summary
A nitride semiconductor laser includes an electrically conductive support substrate with a primary surface of a gallium nitride based semiconductor, an active layer provided above the primary surface, and a p-type cladding region provided above the primary surface. The primary surface is inclined relative to a reference plane perpendicular to a reference axis extending in a direction of the c-axis of the gallium nitride based semiconductor. The p-type cladding region includes first and second p-type Group III nitride semiconductor layers. The first p-type semiconductor layer comprises an InAlGaN layer including built-in anisotropic strain. The second p-type semiconductor layer comprises semiconductor different from material of the InAlGaN layer. The first nitride semiconductor layer is provided between the second p-type semiconductor layer and the active layer. The second p-type semiconductor layer has a resistivity lower than that of the first p-type semiconductor layer.