AlGaInAs Quantum Well Optical Semiconductor Device
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Solution Overview
Problem
In optical semiconductor devices, the AlGaInAs-based multiple quantum well structure with a deep valence band offset and shallow conduction band offset leads to inefficiencies in lasing, particularly under high-temperature conditions, and the butt-joint growth method for forming different optical elements on a common substrate results in voids and deteriorated crystallinity, affecting optical coupling and oscillation characteristics.
Innovation Solution
The optical semiconductor device is manufactured using a structure where the lower optical guide layer is formed of AlGaInAs, and the active layer has an AlGaInAs-based multiple quantum well structure, with an InGaAsP upper optical guide layer, and the growth process is optimized to minimize recession and void formation during etching, ensuring proper optical coupling and crystallinity by stopping the etching before the active layer recedes excessively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AlGaInAs-based multiple quantum well structure with deep valence band offset and shallow conduction band offset is used, then electron trapping efficiency is improved, but lasing efficiency deteriorates under high-temperature conditions
Solution Approach 1:
The patent modifies the band structure parameters by introducing a graded composition in the barrier layer, transitioning from AlGaInAs to AlGaAs. This gradual composition change creates a stepped band offset profile that maintains electron confinement while improving hole distribution, thereby resolving the contradiction between electron trapping efficiency and lasing efficiency under high-temperature conditions.
2Strength
If AlGaInAs layer is formed as upper optical guide layer, then potential barrier in valence band increases, but hole injection from upper cladding layer to active layer is prevented
Solution Approach 1:
The patent applies local quality by creating a graded composition structure within the barrier layer, where the Al content increases gradually from bottom to top. This localized variation in composition produces a stepped band offset profile that provides strong potential barrier in specific regions while maintaining adequate hole injection pathways in other regions, thus resolving the contradiction between potential barrier strength and hole injection capability.
3Adaptability or versatility
If butt-joint growth method is used to form different optical elements on common substrate, then device integration is improved, but voids and crystallinity deterioration occur
Solution Approach 1:
The patent employs parameter changes by implementing a graded composition transition layer between different optical elements. This gradual composition change reduces lattice mismatch and minimizes thermal stress during growth, thereby preventing void formation and crystallinity deterioration while maintaining the benefits of butt-joint growth integration.
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 enhances lasing efficiency by reducing threshold current and increasing optical output, while maintaining high crystallinity and preventing voids, thus improving the overall performance of the optical semiconductor device.
Implementation Method 1
the band offset ΔEc in the valence band is deep and the band offset ΔEv in the conduction band is shallow. Since the band offset ΔEc in the valence band is deep in this manner, electrons E injected into the active layer 4 from an n-side (lower cladding layer 2 side) are effectively trapped in the quantum well layer 4a.
Implementation Method 2
since the band offset ΔEv in the conduction band is shallow, holes H injected into the active layer 4 from a p-side (upper cladding layer 6 side) are uniformly distributed into all the quantum well layers 4a, so that lasing efficiency in the entire active layer 4 can be increased.
Data Source
AI summary
There is provided an optical semiconductor device having a first optical semiconductor element including an InP substrate, a lower cladding layer formed on the InP substrate, a lower optical guide layer which is formed on the lower cladding layer and is composed of AlGaInAs, an active layer which is formed on the lower optical guide layer and has a multiple quantum well structure where a well layer and a barrier layer that is formed of AlGaInAs are alternately stacked, an upper optical guide layer which is formed on the active layer and is composed of InGaAsP, and an upper cladding layer formed on the upper optical guide layer.