GaN VCSEL Silicon-Diffusion Current Blocking Layer
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Solution Overview
Problem
The development of GaN-based vertical cavity surface-emitting lasers has been hindered by the lack of lattice-matched GaN substrate materials and low gain in the active layer, requiring an improved current confinement structure to enhance carrier concentration and reduce laser threshold.
Innovation Solution
A silicon-diffusion defined current blocking layer is used to confine current flow, converting P-type gallium nitride to N-type gallium nitride through silicon diffusion, creating a three-dimensional current confinement structure that reduces the optical mode field diameter and enhances gain, thereby achieving single-mode operation and low spectral width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional current confinement structures are used in GaN-based VCSELs, then the device structure is simpler, but the carrier concentration is insufficient and laser threshold is high
Solution Approach 1:
The patent applies local quality by creating a silicon-diffused current blocking layer with specific spatial distribution. The silicon diffusion is localized to the aperture region where current confinement is needed, while maintaining different material properties in different zones: the diffused silicon region provides high resistivity for current blocking, while the undiffused regions maintain their original properties. This localized modification achieves effective current confinement and carrier concentration enhancement without requiring complete structural redesign.
Solution Approach 2:
The patent utilizes parameter changes by controlling the silicon diffusion process parameters including diffusion temperature, time, and silicon source concentration. By adjusting these parameters, the diffusion depth and silicon concentration profile are optimized to achieve the desired electrical properties. The diffusion depth is controlled to be within a specific range (0.5-2.0 μm) to create the current blocking effect while maintaining optical quality, and the silicon concentration is optimized to achieve high resistivity in the blocking region.
2Shape
If the optical mode field diameter is reduced to achieve single-mode operation, then the beam quality improves, but the current confinement becomes more difficult
Solution Approach 1:
The patent applies local quality by creating a silicon-diffused current blocking layer with specific spatial distribution. The silicon diffusion is localized to the aperture region where current confinement is needed, while maintaining different material properties in different zones: the diffused silicon region provides high resistivity for current blocking, while the undiffused regions maintain their original properties. This localized modification achieves effective current confinement and carrier concentration enhancement without requiring complete structural redesign.
Solution Approach 2:
The patent transitions from two-dimensional planar current confinement to three-dimensional vertical confinement by diffusing silicon into the depth of the active layer. The diffusion creates a vertically extended current blocking region that effectively confines current in the vertical dimension, enabling better control of current density distribution and achieving single-mode operation with improved beam quality.
3Reliability
If silicon diffusion is used to create current blocking layer, then the current confinement effect is enhanced, but the fabrication process becomes more complex
Solution Approach 1:
The patent uses silicon as an intermediary element to achieve current confinement. Instead of directly modifying the GaN material properties or creating complex heterostructure interfaces, silicon is introduced as a diffusion species that acts as a mediator to create the desired electrical properties. The silicon atoms diffuse into the GaN lattice and create localized regions of high resistivity, serving as an intermediary mechanism to achieve current blocking without direct mechanical or structural intervention.
Solution Approach 2:
The patent utilizes parameter changes by controlling the silicon diffusion process parameters including diffusion temperature, time, and silicon source concentration. By adjusting these parameters, the diffusion depth and silicon concentration profile are optimized to achieve the desired electrical properties. The diffusion depth is controlled to be within a specific range (0.5-2.0 μm) to create the current blocking effect while maintaining optical quality, and the silicon concentration is optimized to achieve high resistivity in the blocking region.
4Manufacturing precision
If the aperture diameter is reduced to confine optical mode, then the single-mode operation is achieved, but the current density increases and fabrication precision requirements increase
Solution Approach 1:
The patent uses silicon as an intermediary element to achieve current confinement. Instead of directly modifying the GaN material properties or creating complex heterostructure interfaces, silicon is introduced as a diffusion species that acts as a mediator to create the desired electrical properties. The silicon atoms diffuse into the GaN lattice and create localized regions of high resistivity, serving as an intermediary mechanism to achieve current blocking without direct mechanical or structural intervention.
Solution Approach 2:
The patent utilizes parameter changes by controlling the silicon diffusion process parameters including diffusion temperature, time, and silicon source concentration. By adjusting these parameters, the diffusion depth and silicon concentration profile are optimized to achieve the desired electrical properties. The diffusion depth is controlled to be within a specific range (0.5-2.0 μm) to create the current blocking effect while maintaining optical quality, and the silicon concentration is optimized to achieve high resistivity in the blocking region.
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 silicon-diffusion defined current blocking layer effectively reduces the optical mode field diameter, increases gain, and decreases the current threshold, resulting in single-mode VCSELs and low spectral-width RCLEDs with improved beam quality and reduced divergence angle.
Implementation Method 1
heating the silicon thin film to diffuse the silicon into the P-type gallium nitride, converting the P-type gallium nitride into N-type gallium nitride
Data Source
AI summary
This invention discloses a method for the fabrication of GaN-based vertical cavity surface-emitting devices featuring a silicon-diffusion defined current blocking layer (CBL). Such devices include vertical-cavity surface-emitting laser (VCSEL) and resonant-cavity light-emitting diode (RCLED). The silicon-diffused P-type GaN region can be converted into N-type GaN and thereby attaining a current blocking effect under reverse bias. And the surface of the silicon-diffused area is flat so the thickness of subsequent optical coating is uniform across the emitting aperture. Thus, this method effectively reduces the optical-mode field diameter of the device, significantly decreases the spectral width of LED, and produces single-mode emission of VCSEL.