Optical Image Modulator N Electrode Frame Design
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Solution Overview
Problem
Existing optical image modulators face challenges in achieving high-speed operation and uniform frequency response due to high sheet resistance of the N electrode contact layer, which increases the time constant and reduces light reflectance, making it difficult to drive at high frequencies.
Innovation Solution
The optical image modulator design includes an N electrode frame surrounding the PIN diode structure, with a width increased farther away from the N electrode pad to reduce the time constant and parasitic capacitance, allowing operation at high frequencies and uniform frequency response characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fishbone pitch is reduced to reduce sheet resistance, then the sheet resistance is reduced, but a metal shadow is increased due to the further reduced fishbone pitch, thereby reducing light reflectance
Solution Approach 1:
The patent applies parameter changes by modifying the doping density parameter rather than changing the geometric pitch parameter. Instead of reducing the fishbone pitch (which would increase metal shadow and reduce light reflectance), the patent changes the electrical parameter by introducing a first doped region with higher silicon doping density. This achieves the goal of reducing sheet resistance through material property modification rather than geometric modification, thereby avoiding the harmful effect of reduced light reflectance.
2Speed
If the sheet resistance of the N electrode contact layer is reduced to reduce the time constant, then the operation speed is improved, but the quality of the contact layer is reduced and breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating spatially varying doping density within the N electrode contact layer. A first doped region with high silicon doping density (1×10^19 to 1×10^20 atoms/cm³) is formed to reduce local sheet resistance and thereby reduce the overall time constant for fast operation. Simultaneously, a second doped region with lower silicon doping density (1×10^18 to 1×10^19 atoms/cm³) is formed to maintain overall layer quality and breakdown voltage. This local differentiation allows the system to achieve high-speed operation without sacrificing 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 design enables the optical image modulator to operate at frequencies of several tens of MHz, such as 40 MHz or more, with reduced parasitic capacitance and improved light reflectance, facilitating high-resolution 3D image capturing and other applications.
Implementation Method 1
a lower distributed Bragg reflection (DBR) layer formed on the N electrode contact layer; an upper DBR layer formed on the quantum well layer
Data Source
AI summary
An optical image modulator and a method of manufacturing the same. The optical image modulator includes a substrate, an N electrode contact layer formed on the substrate, a lower distributed Bragg reflection (DBR) layer, a quantum well layer, an upper DBR layer, and a P electrode contact layer sequentially stacked on the N electrode contact layer, a P electrode formed on the P electrode contact layer, and an N electrode formed on the N electrode contact layer. The N electrode is a frame that surrounds the lower DBR layer.