VCSEL Array with TCO Electrodes and Non-Native Substrate
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Solution Overview
Problem
The challenge lies in creating a Vertical-Cavity Surface-Emitting Laser (VCSEL) array that is directly row-column addressable while maintaining high thermal conductivity without restrictions on emission wavelength, as existing solutions like multi-layer sub-mounts and active matrix switches interfere with heat flow and limit efficiency due to n-doping-induced free carrier absorption.
Innovation Solution
The proposed solution involves a semiconductor layer with first and second metal strips arranged in orthogonal directions, allowing for independent addressing of active regions through apertures and mesa structures, eliminating the need for complex sub-mounts and matrix switches, and using non-native substrates like Al2O3 or SiC to enhance thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multi-layer sub-mounts or active matrix switches are used to enable row-column addressing, then addressing complexity is reduced, but thermal conductivity deteriorates due to interference with heat flow
Solution Approach 1:
The patent segments the electrical addressing function from the thermal conduction path by using transparent conductive oxide (TCO) layers that are optically and thermally transparent. The TCO layers are patterned into row and column electrodes that intersect above the VCSEL array, allowing electrical addressing without interfering with the thermal path from the VCSELs to the heat sink.
Solution Approach 2:
The patent introduces transparent conductive oxide (TCO) layers as intermediary elements between the electrical addressing system and the VCSEL array. These TCO layers serve as both electrical conductors for row-column addressing and thermal/optical transparent windows, mediating between the conflicting requirements of electrical isolation and thermal conduction.
2Reliability
If n-type substrates are used to minimize defect density, then VCSEL performance is improved, but free carrier absorption increases at longer wavelengths due to n-doping
Solution Approach 1:
The patent extracts the substrate from the optical path by using a suspended membrane structure where the VCSELs are formed on a thin membrane that is released from the bulk substrate. This allows the use of n-type substrates for low defect density while removing the n-doped material from the optical path, eliminating free carrier absorption at longer wavelengths.
Solution Approach 2:
The patent changes the physical state and position of the substrate material by transforming it from a solid bulk substrate into a suspended thin membrane structure. This parameter change allows the substrate to provide mechanical support and low defect density while being optically transparent and thermally conductive.
3Temperature
If p-side down mounting is used to minimize temperature rise, then thermal management is improved, but complex multi-layer sub-mount construction is required for electrical isolation
Solution Approach 1:
The patent merges the electrical isolation function with the membrane structure itself by forming the VCSELs directly on the suspended membrane with integrated TCO electrodes. This eliminates the need for separate complex multi-layer sub-mount structures, as the membrane and addressing electrodes are formed as an integrated unit.
Solution Approach 2:
The suspended membrane structure serves multiple functions simultaneously: it provides mechanical support for the VCSELs, acts as a thermal conduction path to the heat sink, enables optical transparency, and facilitates electrical addressing through integrated TCO electrodes. This multi-functionality eliminates the need for separate specialized components.
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 enables efficient heat dissipation and independent operation of each VCSEL element, improving thermal conductivity and reducing free carrier absorption, thus enhancing the VCSEL array's performance and flexibility in emission wavelength.
Implementation Method 1
using non-native substrates like Al2O3 or SiC to enhance thermal conductivity
Implementation Method 2
a semiconductor layer having a plurality of active regions adapted to emit light independently
Data Source
AI summary
Optical devices and systems are depicted and described herein. One example of the optical system is disclosed to include a semiconductor layer, a first metal strip positioned adjacent to a first surface of the semiconductor layer, a second metal strip positioned adjacent to a second surface of the semiconductor layer that opposes the first surface of the semiconductor layer, and a third metal strip positioned adjacent to the second surface of the semiconductor layer. In one example, the first metal strip includes a first aperture positioned adjacent to a first active region in the semiconductor layer and second aperture positioned adjacent to a second active region in the semiconductor layer. The second metal strip overlaps the first metal strip in proximity with the first active region and not the second active region and the third metal strip is oriented substantially parallel with the second metal strip.