Recess-Etched VCSEL Structure for Optical and Current Confinement
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Solution Overview
Problem
Existing VCSEL technologies face challenges with poor optical confinement due to thermal lensing effects and damage to the crystal structure, leading to reduced transverse current confinement and manufacturing reproducibility issues.
Innovation Solution
A VCSEL design featuring a recess-etched resistive structure with a resistive portion and an etched window region, providing current blocking and optical index guiding or anti-guiding, manufactured without a wet oxidation process for improved reproducibility and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If proton implantation is used to create high resistance region, then current confinement is improved, but optical confinement deteriorates due to lack of index change and thermal lensing effects
Solution Approach 1:
The device is segmented into distinct functional regions: a central active region with low resistance for current injection, surrounded by a high resistance region formed by proton implantation, which is further surrounded by an oxide region for optical confinement. This segmentation allows each region to perform its specific function optimally without interfering with others.
Solution Approach 2:
The invention uses a composite structure combining different materials and regions: GaAs-based semiconductor layers, proton-implanted high resistance regions, and aluminum oxide confinement layers. Each material contributes specific properties - the semiconductor provides lasing functionality, the implanted region provides electrical isolation, and the oxide provides optical confinement through index guiding.
2Reliability
If oxide confinement VCSEL array is used, then optical confinement is achieved, but device density deteriorates due to large lateral dimension requirements
Solution Approach 1:
The invention transitions from relying solely on lateral oxide dimensions for confinement to using vertical cavity resonance conditions. By controlling the vertical cavity length and using distributed Bragg reflectors, optical confinement is achieved in the vertical dimension, allowing much smaller lateral dimensions and higher device density.
Solution Approach 2:
The invention changes the confinement mechanism from lateral oxide aperture size to vertical cavity resonance parameters. By adjusting the vertical cavity length, mirror reflectivities, and oxide layer thickness, optical confinement is achieved with much smaller lateral dimensions, enabling high-density arrays with center-to-center distances as small as 10 micrometers.
3Ease of operation
If wet oxidation process is used for oxide formation, then current blocking is achieved, but manufacturing precision deteriorates due to poor size control and non-uniformity
Solution Approach 1:
The invention replaces the chemical wet oxidation process with a physical deposition process for forming the oxide confinement layer. This substitution allows precise control of oxide thickness through deposition parameters rather than chemical reaction kinetics, significantly improving size control and uniformity across wafers.
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 proposed VCSEL design achieves enhanced optical confinement, increased maximum output power, and improved reliability with lower thermal resistance and less internal strain, while allowing for highly dense VCSEL arrays without the need for a dopant diffusion process.
Implementation Method 1
a resistive structure located between the upper cavity spacer layer and the second mirror region, wherein the resistive structure comprises: a resistive portion in the outer region and an etched portion located in the inner region of the vertical resonant cavity, such that a conducting channel is formed in the inner region
Implementation Method 2
the placement and thickness of the resistive structure is configured to provide optical index guiding or anti-guiding
Implementation Method 3
a first mirror region forming a lower distributed Bragg reflector; a second mirror region located over the upper cavity spacer layer, wherein the second mirror region forms an upper distributed Bragg reflector, and wherein the upper distributed Bragg reflector and the lower distributed Bragg reflector define a vertical resonant cavity
Data Source
AI summary
A semiconductor vertical cavity surface emitting laser (VCSEL), the VCSEL comprising a first mirror region forming a lower distributed Bragg reflector and a second mirror region forming an upper distributed Bragg reflector, the upper distributed Bragg reflector and the lower distributed Bragg reflector defining a vertical resonant cavity comprising an inner region and an outer region. The VCSEL further comprises a resistive structure comprising a resistive portion in the outer region and an etched portion located in the inner region of the vertical resonant cavity, such that a conducting channel is formed in the inner region.