Vertical-Field Ge Photodetector for Faster Carrier Transit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The response speed of Germanium (Ge) waveguide photodetectors in high-speed optical transceivers is limited by the transit time of photogenerated carriers, which is constrained by the distance they travel across the absorption region, and process limitations restrict how much the width of this region can be reduced.
Innovation Solution
The photodetector design positions one electrode beneath the optical absorber and the other near the top, reducing the height of the absorber rather than its width, thereby reducing the travel distance of carriers and improving speed without being limited by process constraints on width reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the width of the absorption region is reduced to reduce carrier travel distance, then the transit time is improved, but process limitations prevent further width reduction
Solution Approach 1:
The patent transitions from reducing the width (lateral dimension) of the absorption region to reducing its height (vertical dimension). By orienting the absorption region vertically between n-type and p-type doped regions, the carrier travel distance is reduced in the vertical direction rather than the lateral direction, thereby avoiding the process limitations that constrain width reduction.
2Speed
If the width of the absorption region is reduced to improve response speed, then the transit time decreases, but the manufacturing precision requirements increase due to process limitations
Solution Approach 1:
The invention changes the dimension in which the absorption region is minimized from lateral width to vertical height. The vertical orientation between doped regions allows for precise control of carrier travel distance through the height dimension, which can be better controlled by standard fabrication processes compared to lateral width reduction.
3Speed
If the absorption region width is minimized to reduce transit time, then the photodetector speed increases, but the device complexity increases due to doping region configuration
Solution Approach 1:
The patent combines the absorption region with n-type and p-type doped regions in a vertical configuration. The absorption region is positioned between the oppositely doped regions, which creates the necessary electric field for rapid carrier collection. This merging of functional regions in the vertical dimension achieves fast response while using standard doping processes.
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 design enhances the speed of the photodetector by reducing the travel distance of carriers, overcoming the limitations on width reduction in existing designs and improving transit times.
Implementation Method 1
converting the optical data streams into the electrical domain
Implementation Method 2
directing a positive charge in the optical absorber towards a first doped region disposed in the substrate and a second doped region disposed in the substrate
Data Source
AI summary
A photodetector includes a substrate, an optical absorber, a first doped region, a second doped region, and a third doped region. The optical absorber is disposed in the substrate and includes a first region and a second region. The first doped region is disposed in the substrate such that the first doped region contacts the second region of the optical absorber. The second doped region is disposed in the substrate such that the second doped region contacts the second region of the optical absorber. The second region of the optical absorber is positioned between the first doped region and the second doped region. The third doped region is disposed in the substrate and has an opposite doping relative to the first doped region and the second doped region. The first region of the optical absorber is positioned between the third doped region and the second region of the optical absorber.