VCSEL With Through-Substrate Vias for Low Resistance Contacts
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Solution Overview
Problem
Conventional vertical cavity surface emitting lasers (VCSELs) face design challenges in connecting to a current source due to the high resistance of ohmic contacts made through the substrate, which complicates electrical connections.
Innovation Solution
The VCSEL design incorporates electrically conductive vias that pass through the substrate to provide ohmic contact with both distributed Bragg reflectors, allowing for low resistance electrical connections on the substrate side, enabling efficient current supply and laser emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ohmic contacts are made through the substrate in conventional VCSELs, then electrical connections are simplified, but the resistance of the contacts becomes high
Solution Approach 1:
The invention divides the electrical connection path into multiple segments: via holes through the substrate, conductive material filling, and contact regions on the DBRs. This segmentation allows each component to be optimized independently, reducing overall resistance while maintaining connection reliability
Solution Approach 2:
Electrically conductive material is introduced as an intermediary substance within via holes to create low-resistance pathways between the substrate and DBRs. This mediator replaces the high-resistance direct-through-substrate contact with a optimized conductive path
2Device complexity
If conventional VCSEL connection methods are used, then device structure is simple, but design challenges arise in connecting to current source
Solution Approach 1:
The invention moves electrical contacts from the top surface to the substrate side (backside), utilizing the vertical dimension to improve accessibility. This dimensional repositioning allows current source connections to be made from the substrate side, simplifying integration with drive electronics
Solution Approach 2:
Via holes and conductive material are prepared in advance during fabrication, creating pre-established low-resistance contact paths. This preliminary preparation eliminates the need for complex post-fabrication connection procedures
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 configuration reduces the resistance of electrical connections, facilitating reliable and efficient operation of the VCSEL by providing accessible ohmic contacts on the substrate side, thereby addressing the design challenges of conventional VCSELs.
Implementation Method 1
electrically conductive vias that pass through the substrate and provide ohmic contact with the DBRs
Data Source
AI summary
In an illustrative embodiment, a VCSEL comprises a substrate, a first DBR on a first major surface of the substrate, an active region on the first DBR, a second DBR on the active region, and electrically conductive vias that pass through the substrate and provide ohmic contact with the DBRs so that electrical connections to both DBRs are available on the substrate side of the VCSEL. The VCSEL is formed by forming a first DBR on a first major surface of a substrate, forming an active region on the first DBR, forming a second DBR on the active region, thinning the substrate, making a first via hole through the substrate to the first DBR, making a second via hole through the substrate and the first DBR, filling the first via hole with an electrically conducting material to contact the first DBR, filling the second via hole with an electrically conducting material, and coupling the second via hole to the second DBR.