Air-Bridge Photodetector Layout for Faster Beating Spectroscopy
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Solution Overview
Problem
The existing photodetectors require an increase in response speed while ensuring output signal intensity and reliability, and the wavelength scanning range in beating spectroscopy devices needs to be widened.
Innovation Solution
A photodetector with a semiconductor substrate and a mesa portion that includes alternately stacked absorption and transport regions, connected by air bridge wiring to reduce inductance and parasitic capacitance, ensuring faster response and maintaining signal intensity, integrated into a beating spectroscopy device to widen the wavelength scanning range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect the first contact layer and the first electrode, then the connection is reliable, but the wiring length is long which increases inductance and reduces response speed
Solution Approach 1:
The patent extracts the bonding wire from the system and replaces it with an air bridge wiring structure that directly connects the first contact layer to the first electrode through air, eliminating the need for external wire bonding and reducing inductance
Solution Approach 2:
The connection transitions from a planar wire bonding approach to a three-dimensional air bridge structure that extends vertically and horizontally, optimizing the connection path to reduce inductance while maintaining reliability
2Speed
If the area of the mesa portion is reduced to reduce parasitic capacitance and increase response speed, then the response speed increases, but the output signal intensity decreases
Solution Approach 1:
The mesa portion is designed with an asymmetric rectangular shape where the length in the optical waveguide direction is significantly greater than the width, creating an optimized aspect ratio that reduces parasitic capacitance while maintaining sufficient light absorption area for signal intensity
Solution Approach 2:
The patent optimizes the geometric parameters of the mesa portion, specifically setting the length to be greater than the width in the optical waveguide direction, which changes the capacitance characteristics while preserving light absorption efficiency
3Reliability
If the air bridge wiring is made wide to reduce inductance and ensure strength, then the inductance decreases and reliability improves, but the area occupied increases
Solution Approach 1:
The air bridge wiring utilizes three-dimensional space by extending in both horizontal and vertical dimensions, allowing the wiring to achieve sufficient cross-sectional area for low inductance and high strength while occupying minimal planar area on the substrate
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 photodetector achieves increased response speed, ensures output signal intensity, and enhances reliability, allowing for a broader wavelength scanning range in beating spectroscopy.
Implementation Method 1
absorption regions that absorb detection light through intersubband absorption
Implementation Method 2
Inductance can be reduced by shortening the wiring length
Implementation Method 3
parasitic capacitance can be reduced by reducing the area of the mesa portion
Data Source
AI summary
A photodetector includes: a semiconductor substrate; a mesa portion formed on a major surface of the semiconductor substrate to extend along an optical waveguide direction; a first contact layer; a second contact layer; a first electrode; and an air bridge wiring electrically connected to the first contact layer and the first electrode. When viewed in a direction perpendicular to the major surface of the semiconductor substrate, a length of the mesa portion in the optical waveguide direction is longer than a length of the mesa portion in a direction perpendicular to the optical waveguide direction. The air bridge wiring is led out from the first contact layer to one side in the direction perpendicular to the optical waveguide direction, and is bridged between the first contact layer and the first electrode.