Quantum Well Optical Modulator With Al-Free InGaPSb Barriers
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Solution Overview
Problem
Optical modulators using quantum well structures face challenges in achieving both high-speed operation and large extinction ratio due to band discontinuity issues, particularly when the well layer thickness exceeds 6 nm, and there are concerns regarding long-term reliability, especially with materials containing Al.
Innovation Solution
An optical modulator is developed with a multiple quantum well structure using InAsP as the well layer and InGaPSb as the barrier layer, which allows for high-speed operation by optimizing band discontinuity and long-term reliability without using Al-containing materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the well layer thickness is increased to improve light absorption and extinction ratio, then the extinction ratio is improved, but the operation speed decreases due to increased carrier transit time
Solution Approach 1:
The patent changes the material composition parameters of the barrier layer, specifically incorporating Sb (antimony) to adjust the band discontinuity. By optimizing the Sb content and composition ratio in the InGaAsSb barrier layer, the patent achieves appropriate band alignment that enables both thick well layers for high extinction ratio and fast carrier extraction for high operation speed
Solution Approach 2:
The patent uses composite material structure with InGaAsSb barrier layer combined with InAsP well layer. This composite structure leverages the specific properties of each material: InAsP provides strong light absorption in the 1.3μm wavelength region, while InGaAsSb provides appropriate band discontinuity for fast carrier extraction, resolving the contradiction between extinction ratio and operation speed
2Reliability
If Al-containing materials are used in the quantum well structure to improve band discontinuity and extinction ratio, then the extinction ratio is improved, but long-term reliability deteriorates due to material stability issues
Solution Approach 1:
The patent replaces Al-containing materials with Al-free InGaAsSb materials. Although InGaAsSb requires precise composition control, it provides comparable or superior performance with improved long-term stability, effectively substituting a material with known reliability issues (Al-containing) with a more stable alternative
Solution Approach 2:
The patent changes the material composition by eliminating Al and using InGaAsSb with optimized Sb content. This parameter change in material composition achieves the desired band discontinuity and extinction ratio while ensuring long-term device reliability through the use of stable Al-free materials
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 optical modulator achieves high-speed operation and improved extinction ratio while ensuring long-term reliability, facilitating the construction of efficient optical communication networks.
Implementation Method 1
when the external electric field is applied, band gap energy E2 of the well layer becomes smaller than E1. This phenomenon is known as quantum confined Stark effect (QCSE)
Data Source
AI summary
An optical modulator is formed on a substrate constituted of InP, and an active layer is formed on the substrate via a lower InP layer constituted of InP. The active layer has a multiple quantum well structure including a well layer constituted of a group III-V compound semiconductor including In, As, and P as constituent elements and a barrier layer constituted of a group III-V compound semiconductor including In, Ga, P, and Sb as constituent elements.