Light Modulators Comprising Si-Ge Quantum Well Layers

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This patent describes advanced optical modulators made from silicon-germanium (Si-Ge) quantum well layers that are engineered on specially prepared silicon substrates. These modulators use a combination of Si-Ge layers with varying germanium content to tailor their optical properties, making them effective for modulating light at wavelengths used in fiber optic communications (1.3 and 1.55 μm). The devices are manufactured efficiently using low-energy plasma-enhanced chemical vapor deposition (LEPECVD), and operate using several physical effects, such as the quantum-confined Stark effect and Franz-Keldysh effect, to control how light is absorbed and transmitted.

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• High-speed optical modulators in fiber optic communication networks, including the telecom industry.
• On-chip optical interconnects for high-performance computing systems (e.g., data centers).
• Integrated optoelectronic circuits for communication between electronic and photonic devices on a single silicon chip.
• Optical switches or variable optical attenuators for advanced photonic networks.
• Sensors utilizing optical modulation for precise measurement applications.

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• Enables efficient and high-speed light modulation at telecom wavelengths (1.3/1.55 μm) compatible with fiber optics.
• Utilizes silicon-compatible materials and manufacturing methods, supporting easy integration with existing semiconductor processes.
• Provides strain-compensated quantum well structures, ensuring high material quality and device performance.
• Employs fast and scalable LEPECVD fabrication, potentially reducing production costs and time.
• Supports several physical modulation mechanisms, offering flexibility in device design and operation.

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Patent Abstract

Optical modulators include active quantum well structures (200) coherent with pseudosubstrates (100) comprising relaxed buffer layers (104, 106, 108, 110) on a silicon substrate (102). In a preferred method the active structures, consisting of Si1-x Gex barrier and well layers with different Ge contents x, are chosen in order to be strain compensated. The Ge content in the active structures may vary in a step-wise fashion along the growth direction or in the form of parabolas within the quantum well regions. Optical modulation may be achieved by a plurality of physical effects, such as the Quantum Confined or Optical Stark Effect, the Franz-Keldysh Effect, exciton quenching by hole injection, phase space filling or temperature modulation. In a preferred method the modulator structures are grown epitaxially by low-energy plasma-enhanced chemical vapor deposition (LEPCVD).