VCSEL with InGaAs Wells and GaAsP Barriers

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Solution Overview

Problem

Conventional VCSELs with GaAs quantum wells and AlGaAs barriers suffer from reduced optical confinement, high temperature performance, and reliability due to carrier leakage and oxidation of aluminum in the barrier layers, leading to short lifetimes and reduced performance.

Innovation Solution

The VCSEL employs compressively strained InxGa1-xAs quantum wells and tensile strained GaAs1-yPy barriers with increased bandgap discontinuities, along with separate confinement heterostructure layers and a mesa structure with passivation, to enhance optical confinement and high-temperature performance, and includes reflecting mirror stacks with high Al content for improved reliability and communication speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If AlGaAs barrier layers are used in the quantum-well structure, then the VCSEL can achieve 850 nm wavelength emission, but the aluminum in the barrier layer oxidizes in moisture/humidity ambient forming defects or dislocations that reduce the lifetime

Engineering Contradiction:

ImproveVCSEL lifetimeVSAvoidoxidation of aluminum in barrier layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes aluminum-containing materials from the barrier layers and replaces them with GaAsP-based materials. This extraction of the harmful element (Al) eliminates the oxidation problem while maintaining the required optical and electrical properties for 850 nm VCSEL operation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses composite material structures including InGaAs quantum wells with GaAsP barrier layers. This composite approach allows optimization of each layer's properties - the InGaAs provides the quantum confinement for 850 nm emission while the GaAsP barriers provide oxidation resistance and appropriate bandgap characteristics.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional GaAs quantum wells and AlGaAs barriers are used, then the device structure is simple, but carrier leakage occurs across the barrier layers reducing optical confinement and high temperature performance

Engineering Contradiction:

Improveoptical confinement and high temperature performanceVSAvoidquantum-well structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the compositional parameters of the barrier layers by using GaAsP instead of AlGaAs, and optimizes the InGaAs quantum well composition (with x ranging from 0.03 to 0.15). These parameter changes increase the bandgap discontinuity at the interfaces, thereby reducing carrier leakage while maintaining structural feasibility.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different material compositions to different regions: InGaAs for quantum wells where carrier confinement is needed, and GaAsP for barrier layers where oxidation resistance and high bandgap are required. This local optimization of material properties addresses carrier leakage without uniformly increasing device complexity.

Inventive Principle:

Principle #3Local quality

3Reliability

If the quantum-well structure uses fixed bandgap materials, then the manufacturing process is straightforward, but the conduction band and valence band discontinuities are small causing carrier leakage and reduced performance

Engineering Contradiction:

Improvecarrier confinement and performanceVSAvoidquantum-well structure fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs parameter optimization within the InGaAs and GaAsP material systems, where the composition ratios (x and y values) are carefully controlled during growth. This allows tuning of the bandgap and band alignment to achieve optimal carrier confinement while maintaining compatibility with existing semiconductor fabrication processes.

Inventive Principle:

Principle #35Parameter changes

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

The solution provides improved optical confinement, increased communication speed, and extended lifespan of the VCSEL, while allowing for high-temperature operation and resistance to environmental factors like moisture and humidity.

Implementation Method 1

compressively strained InxGa1-xAs quantum wells; two or more tensile strained GaAs1-yPy barriers

Methodology Applied

Scientific EffectStrain:

Implementation Method 2

increased bandgap discontinuities

Methodology Applied

Scientific EffectBandgap discontinuity:

Implementation Method 3

generate light with a wavelength of 850 nm

Methodology Applied

Scientific EffectLight emission: Light

Implementation Method 4

electrons and holes combine to generate light

Methodology Applied

Scientific EffectElectron-hole recombination:

Implementation Method 5

reflecting mirror stacks with high Al content

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 6

mesa structure with passivation

Methodology Applied

Scientific EffectPassivation:

Data Source

PatentUS20160276805A1Vertical cavity surface emmiting laser

Publication Date: 2016.09.22 WELLS FARGO BANK NA

AI summary

A VCSEL according to the invention, configured to emit a light having about 850 nm wavelength, comprises an active region which comprises one or more InxGa1-xAs quantum wells; two or more GaAs1-yPy barriers bonding to the one or more quantum wells; and x ranges from 0.05 to 0.1, and y ranges from 0.2 to 0.29. The VCSEL has increased optical confinement and high transmission speed, good reliability characteristics, high-temperature performance, and long life time.