Microstructure Enhanced Photodetectors for High Speed Data
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Solution Overview
Problem
Current photodiodes and avalanche photodiodes for specific optical wavelengths, particularly 850-950 nm and 1550-1650 nm, lack commercial availability with data rates of at least 25 Gb/s and are not monolithically integrated with CMOS/BiCMOS silicon electronics on a single chip, limiting their application in high-speed data transmission and communication.
Innovation Solution
Development of a single-chip structure with a photosensitive portion and active CMOS or BICMOS electronic circuit, featuring a P-doped region, N-doped region, and an I-region of low-doped or undoped semiconductor material, with microstructure holes to enhance absorption and quantum efficiency, allowing for monolithic integration and high data rate operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the silicon absorption region is increased to detect longer wavelengths, then quantum efficiency is improved, but bandwidth becomes too low for high-speed applications
Solution Approach 1:
The patent introduces microstructure holes (three-dimensional features) into the silicon absorption region, transforming the flat two-dimensional structure into a three-dimensional microstructured structure. This dimensional change increases the effective light absorption path length and surface area without increasing the overall device thickness, thereby improving quantum efficiency while maintaining high bandwidth capability.
2Productivity
If photodiodes are designed for high data rates of at least 25 Gb/s, then productivity is improved, but commercial availability and monolithic integration with CMOS electronics deteriorate
Solution Approach 1:
The patent merges the photodiode structure with CMOS/BiCMOS electronic circuits on a single silicon chip, achieving monolithic integration. The microstructure hole photodiodes are fabricated using CMOS-compatible processes, combining high-speed optical detection capabilities with electronic signal processing in one integrated device, thereby enabling commercial availability and simplifying manufacturing.
3Measurement precision
If microstructure holes are added to enhance absorption, then quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The patent employs a porous-like microstructure by creating an array of holes in the silicon absorption region. This microstructured approach increases the effective surface area and light absorption path length, improving external quantum efficiency. The periodic hole structure can be fabricated using standard semiconductor processing techniques, managing complexity through regular patterns.
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 enables high-speed data transmission with improved external quantum efficiency and reduced parasitics, enhancing optical absorption and processing capabilities for CMOS/BiCMOS applications, suitable for both short and long-haul optical data transmission and LiDAR applications.
Implementation Method 1
microstructure holes to enhance absorption and quantum efficiency
Implementation Method 2
photosensitive portion... comprises at least one photodetector... generating electrical signals in response to illumination
Data Source
AI summary
Lateral and vertical microstructure enhanced photodetectors and avalanche photodetectors are monolithically integrated with CMOS/BiCMOS ASICs and can also be integrated with laser devices using fluidic assembly techniques. Photodetectors can be configured in a vertical PIN arrangement or lateral metal-semiconductor-metal arrangement where electrodes are in an inter-digitated pattern. Microstructures, such as holes and protrusions, can improve quantum efficiency in silicon, germanium and III-V materials and can also reduce avalanche voltages for avalanche photodiodes. Applications include optical communications within and between datacenters, telecommunications, LIDAR, and free space data communication.