Tunable VCSEL Etched Post Structure for Optical and Current Confinement
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Solution Overview
Problem
Existing VCSEL technologies face challenges in achieving efficient electrical and optical confinement, particularly for long-wavelength VCSELs, due to limitations in selective oxidation and reliance on ion implantation or buried tunnel junctions, which can introduce reliability issues.
Innovation Solution
The development of a fully epitaxial grown tunable VCSEL with an etched post between the active region and a sacrificial layer, followed by regrowth of the sacrificial layer and HCG layer around the post, provides both lateral electrical current and optical confinement, resulting in increased efficiency and reduced cavity volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective oxidation is used to form current aperture, then electrical confinement is improved, but optical confinement deteriorates due to index mismatch and reliability issues
Solution Approach 1:
The patent changes the refractive index parameter by filling the etched post with a dielectric material having a specific index (e.g., SiO2 with n≈2.0) to achieve optimal optical confinement. This parameter adjustment resolves the contradiction by providing both electrical isolation and optical waveguide formation without the reliability issues of selective oxidation
Solution Approach 2:
The patent employs a composite structure combining semiconductor materials (GaAs, AlGaAs) with dielectric materials (SiO2, Si3N4) in the post region. This composite approach enables simultaneous electrical confinement through the etched post geometry and optical confinement through the dielectric material's refractive index, eliminating the need for selective oxidation
2Reliability
If ion implantation or buried tunnel junctions are used for current confinement, then electrical confinement is improved, but reliability deteriorates due to introduced defects
Solution Approach 1:
The patent extracts the problematic ion implantation and buried tunnel junction steps from the fabrication process. Instead, it uses a simpler etched post structure that provides current confinement through geometric definition and dielectric filling, eliminating the reliability-damaging defects while maintaining current confinement efficiency
Solution Approach 2:
The patent replaces complex, defect-prone structures (ion-implanted regions, buried tunnel junctions) with a simpler etched post filled with dielectric material. This simpler structure achieves the same current confinement function without introducing reliability issues, effectively using a more robust but simpler approach
3Power
If larger cross-sectional area is used, then output power is improved, but threshold current density worsens
Solution Approach 1:
The patent applies local quality enhancement by concentrating the optical mode and electrical current in the etched post region. The dielectric-filled post creates a high-index contrast waveguide that confines both optical and electrical fields locally, enabling large-area devices to maintain low threshold current densities while achieving high output power
4Productivity
If smaller cavity volume is achieved through etched post, then efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the VCSEL structure by introducing an etched post that divides the cavity into distinct regions: an active region above the post and a lower region around the post. This segmentation enables independent optimization of optical confinement and electrical injection, achieving high efficiency while using standard semiconductor fabrication techniques
Solution Approach 2:
The etched post filled with dielectric material acts as an intermediary structure that simultaneously provides electrical isolation, optical confinement, and mechanical support. This intermediary element resolves the contradiction by enabling small cavity volume for high efficiency while using well-established etching and deposition processes
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 enhances the efficiency of VCSELs by ensuring tight overlap of optical and electrical confinement, enabling high-speed modulation and coherent communication while minimizing reliability concerns associated with previous methods.
Implementation Method 1
An etched post between an active region and a sacrificial layer provides lateral electrical current and optical confinement
Implementation Method 2
A regrowth of sacrificial layer and HCG layer is done around the post
Data Source
AI summary
A light emitting apparatus includes a VCSEL laser. The VCSEL laser has one or more active regions with quantum wells and barriers. The active regions are surrounded by one or more p-n junctions. The one or more active regions can include a selected shape structure, as well as one or more tunnel junctions (TJ). One or more apertures are provided with the selected shape structure. One or more buried tunnel junctions (BTJ) or oxide confine apertured, additional TJ's, planar structures and or additional BTJ's are created during a regrowth process that is independent of a first growth process. A VCSEL output is determined in response to a monitoring application of the VCSEL. The VCSEL has an HCG grating and a bottom DBR. An etched post is between an active region and a sacrificial layer.