Series-Connected VCSEL Arrays with Via Interconnects
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Solution Overview
Problem
Current VCSEL designs face challenges in achieving high-power emission below 900 nm due to substrate absorption and thermal management limitations, making it difficult to fabricate efficient bottom-emitting VCSELs with high packing density and reliable thermal dissipation.
Innovation Solution
The VCSEL array is designed with a series connection of devices through vias for improved thermal management and reduced joule heating, where the GaAs substrate is removed, and contacts are annealed before flip-chip bonding to minimize absorption and enhance power efficiency, allowing for dense, high-power VCSEL arrays with efficient heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If VCSELs are connected in parallel with planar contacts, then fabrication is simplified, but joule heating increases and power efficiency decreases
Solution Approach 1:
The patent segments the electrical connection path by introducing vias that divide the current flow into multiple vertical paths through the substrate. This segmentation reduces the current density in any single planar contact region, thereby reducing joule heating while maintaining the overall parallel connection architecture for fabrication simplicity.
Solution Approach 2:
The patent transitions from purely planar (2D) contacts to a three-dimensional connection architecture by adding vertical vias. This dimensional change allows current to flow through multiple layers and paths, distributing the electrical load and reducing resistive heating in any single plane while preserving the parallel interconnection benefits.
2Object-generated harmful factors
If substrate is removed for bottom-emitting VCSELs, then absorption is reduced, but thermal management becomes more difficult
Solution Approach 1:
The patent introduces an intermediary heat sink structure with integrated heat spreaders and thermal interface materials between the VCSEL array and the external cooling system. This intermediary structure efficiently collects heat from the substrate-less VCSELs and transfers it to the cooling system, solving the thermal management challenge created by substrate removal.
Solution Approach 2:
The heat sink structure serves multiple functions: it provides thermal management, mechanical support, and electrical grounding for the substrate-less VCSEL array. This multi-functional design addresses the thermal challenges while simplifying the overall device architecture.
3Loss of energy
If contacts are annealed before flip-chip bonding, then power efficiency increases, but process complexity increases
Solution Approach 1:
The patent performs contact annealing as a preliminary action before flip-chip bonding, ensuring low contact resistance and high power efficiency is achieved prior to final assembly. This preliminary treatment of the contacts eliminates the need for post-bonding annealing steps, actually simplifying the overall process while maintaining high efficiency.
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 enables high-output power VCSEL arrays with reduced joule heating and increased efficiency, allowing for serial connection of devices with manageable input currents and lower operating power, suitable for applications requiring high power and efficiency.
Implementation Method 1
an electrical path to at least one of the plurality of second mirrors is made through a via formed through a depth of the plurality of second mirrors
Implementation Method 2
a heatsink, thermally and mechanically coupled to the second mirror opposite the plurality of active regions
Implementation Method 3
contacts are annealed before flip-chip bonding to minimize absorption and enhance power efficiency
Data Source
AI summary
Vertical Cavity Surface Emitting Laser (VCSEL) arrays with vias for electrical connection are disclosed. A Vertical Cavity Surface Emitting Laser (VCSEL) array in accordance with one or more embodiments of the present invention comprises a plurality of first mirrors, a plurality of second mirrors, a plurality of active regions, coupled between the plurality of first mirrors and the plurality of second mirrors, and a heatsink, thermally and mechanically coupled to the second mirror opposite the plurality of active regions, wherein an electrical path to at least one of the plurality of second mirrors is made through a via formed through a depth of the plurality of second mirrors, and a plurality of VCSELs in the VCSEL array are connected in series.