VCSEL Stress Relief Layer Lattice Mismatch
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Solution Overview
Problem
Vertical cavity surface emitting lasers face decreased electro-optical conversion efficiency due to stress and strain from lattice mismatching and oxidized layer formation, which are exacerbated by continuous electricity conduction.
Innovation Solution
Incorporating low activity energy layers with band gaps smaller than the optical confinement layers and AlGaAs material composition ratios lower than the active layer's, positioned between the active layer and the multilayer reflector layers, to suppress stress and strain propagation and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If different materials are used for the active layer, spacer layers, and DBR layers, then the laser can be manufactured with standard semiconductor processes, but stress and strain are generated due to lattice mismatching which decreases electro-optical conversion efficiency
Solution Approach 1:
The patent introduces a stress relief layer as an intermediary between the active layer and the DBR layers. This intermediate layer has a composition specifically designed to have a lattice constant that reduces the mismatch between the GaAs-based active layer and the AlGaAs-based DBR layers, thereby mediating the stress and preventing degradation of electro-optical conversion efficiency while maintaining manufacturability
Solution Approach 2:
The patent changes the compositional parameter of the stress relief layer to optimize lattice matching. By adjusting the Al composition ratio in the AlGaAs material of the stress relief layer, the lattice constant is tuned to reduce stress propagation to the active layer, thus maintaining high electro-optical conversion efficiency
2Use of energy by moving object
If an oxidized layer is formed to narrow the current aperture, then the current density is increased and power consumption is decreased, but the stress and strain from the oxidized layer are accelerated by electricity conduction which adversely affects the active layer and decreases electro-optical conversion efficiency
Solution Approach 1:
The stress relief layer serves as a mediator between the oxidized layer and the active layer. It absorbs and redistributes the stress generated by the oxidized layer, preventing direct transmission of harmful stress to the active layer while allowing the current aperture narrowing effect to maintain low power consumption
Solution Approach 2:
The stress relief layer provides beforehand cushioning by being positioned between the oxidized layer and the active layer. It preemptively absorbs the stress that would otherwise be transmitted to the active layer during operation, protecting the active layer from degradation even under continuous electricity conduction
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 maintains high electro-optical conversion efficiency even with continuous electricity conduction, enhancing the reliability of the vertical cavity surface emitting laser.
Implementation Method 1
stress and strain are generated due to lattice mismatching
Implementation Method 2
an active layer equipped with a quantum well is formed
Implementation Method 3
first multilayer distributed Bragg reflector (DBR) layer
Data Source
AI summary
A vertical cavity surface emitting laser includes an active layer that includes a quantum well, a first cladding layer and a second cladding layer between which the active layer is interposed. A first multilayer reflector layer is arranged on a side of the first cladding layer opposite to that on which the active layer is arranged. A second multilayer reflector layer is arranged on a side of the second cladding layer opposite to that on which the active layer is arranged. At least one of the first cladding layer and the second cladding layer includes a low activity energy layer having a band gap that is smaller than a smallest band gap of an optical confinement layer for forming the quantum well of the active layer and larger than a band gap of the quantum well.