Germanium Avalanche Photodiode Structure for Lower Bias Voltage
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Solution Overview
Problem
Conventional avalanche photodiodes require high bias voltages, which increases power consumption and complicates their integration into optical communication systems, and their fabrication for use in optical electronics is challenging.
Innovation Solution
A germanium-based avalanche photodiode device is designed with a silicon substrate, doped silicon regions, and a germanium waveguide structure that reduces operating voltage and simplifies manufacturing by using a silicon-on-insulator layer and epitaxial growth to form doped regions, allowing for lateral electrode contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional avalanche photodiodes are used, then they can convert light into electricity with avalanche multiplication, but they require high bias voltages (>25V) which increases power consumption
Solution Approach 1:
The patent changes the material composition parameter by incorporating germanium layers (5-50nm thick) within the silicon avalanche photodiode structure. This material parameter change enables the device to achieve avalanche multiplication at lower bias voltages (5-25V) compared to conventional all-silicon designs, directly reducing power consumption while maintaining the light-to-electricity conversion function
Solution Approach 2:
The patent creates a composite structure combining silicon and germanium materials. The germanium layers are strategically positioned within the silicon substrate to form a hybrid avalanche photodiode that leverages the advantageous properties of both materials: silicon provides the substrate and waveguide functionality, while germanium enhances carrier multiplication efficiency at reduced voltage levels
2Reliability
If conventional avalanche photodiodes are fabricated, then they can achieve avalanche breakdown, but the fabrication process is problematic and fraught with difficulties for integration into optical circuits
Solution Approach 1:
The patent segments the avalanche photodiode fabrication into distinct epitaxial growth stages. The structure is built layer-by-layer using selective epitaxial growth, with each germanium layer deposited at controlled thickness (5-50nm) and specific positions within the silicon stack. This segmented approach enables precise control over material composition and layer thickness, improving fabrication reliability and integrability into optical circuits
Solution Approach 2:
The patent employs preliminary epitaxial growth of silicon layers with specific doping profiles before introducing germanium layers. The silicon-on-insulator substrate is prepared with pre-doped regions, and intermediate silicon layers are grown and doped in advance to create the proper electric field distribution before the germanium avalanche multiplication layers are deposited. This preliminary structuring simplifies the overall fabrication process and improves integration reliability
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 reduces the operating voltage to around 10V, improving power efficiency and simplifying the manufacturing process, making it more suitable for optical communication systems.
Implementation Method 1
The avalanche photodiode is a sensitive semi-conductive electronic device, which exploits the photo-electronic effect to convert light into electricity
Implementation Method 2
Avalanche breakdown is a phenomenon in which, through the application of an electric field, charge carriers cause the production of other charge carriers within a multiplication region of a device
Data Source
AI summary
A germanium based avalanche photo-diode device and method of manufacture thereof. The device including: a silicon substrate; a lower doped silicon region, positioned above the substrate; a silicon multiplication region, positioned above the lower doped silicon region; an intermediate doped silicon region, positioned above the silicon multiplication region; a doped germanium interface layer, positioned above the intermediate doped silicon region; an un-doped germanium absorption region, position above the doped germanium interface layer; an upper doped germanium region, positioned above the un-doped germanium absorption region; and an input silicon waveguide; wherein: the un-doped germanium absorption region and the upper doped germanium region form a germanium waveguide which is coupled to the input waveguide, and the device also includes a first electrode and a second electrode, and the first electrode extends laterally to contact the lower doped silicon region and the second electrode extends laterally to contact the upper doped germanium region.