VCSEL Array Insulating Grooves for Uniform Burn-in Testing
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Solution Overview
Problem
Vertical cavity surface emitting laser arrays face challenges in achieving uniform load current distribution during burn-in tests due to conductive semiconductor layers, leading to inaccurate and costly testing processes.
Innovation Solution
A vertical cavity surface emitting laser array is designed with a semi-insulating semiconductor substrate and insulating regions between adjacent devices, connected by inter-device lines, to ensure uniform load current distribution and prevent leakage, using insulating grooves and high resistance regions formed by ion implantation for enhanced electrical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conductive semiconductor layer is used in the semiconductor substrate, then the laser devices can be connected in series for burn-in testing, but current leakage occurs through the conductive layer causing non-uniform load current distribution
Solution Approach 1:
The semiconductor substrate is divided into multiple isolated regions by insulating grooves that extend from the front surface to the back surface. These grooves physically segment the conductive semiconductor layer into separate regions, preventing current leakage between adjacent laser devices while maintaining series connection capability for burn-in testing.
Solution Approach 2:
Insulating grooves filled with insulating material are introduced as intermediary structures between adjacent laser devices. These grooves act as mediators that electrically isolate the conductive semiconductor layer in different device regions, ensuring that current flows uniformly through each device without leaking into adjacent devices through the substrate.
2Reliability
If insulating grooves are formed to prevent current leakage, then uniform load current distribution is achieved, but manufacturing complexity increases
Solution Approach 1:
The formation of insulating grooves is merged with the existing laser device fabrication process. The grooves are formed by etching through the semiconductor substrate using the same photolithography and etching techniques already employed for creating laser device structures, thereby integrating the insulation feature into the standard manufacturing flow without adding significant process steps.
3Reliability
If the semiconductor substrate is made semi-insulating, then current leakage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring the entire semiconductor substrate to be semi-insulating, insulating grooves are formed only in specific locations between adjacent laser devices. This local approach to electrical insulation provides the necessary current blocking function only where needed, while the rest of the substrate can maintain its standard conductive properties, reducing overall manufacturing precision requirements.
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 allows for accurate and low-cost burn-in testing of vertical cavity surface emitting laser arrays by ensuring uniform load current distribution across all devices, reducing leakage and enabling simultaneous testing under the same conditions.
Implementation Method 1
An insulating region that electrically insulates the two vertical cavity surface emitting laser devices is formed on the semiconductor substrate
Implementation Method 2
insulating grooves and high resistance regions formed by ion implantation for enhanced electrical insulation
Data Source
AI summary
A VCSEL array includes a base substrate, a plurality of VCSEL devices and an inter-device line. Each of the plurality of VCSEL devices is disposed on a front side of the base substrate. The inter-device line connects two of the plurality of VCSEL devices that are adjacent to each other, the two VCSEL devices being connected in series such that forward directions of the two VCSEL devices are the same. An insulating groove that electrically insulates the two VCSEL devices is formed on the base substrate.