Semiconductor Laser Monitor Photodetector Layout for Higher ESD Resistance
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Solution Overview
Problem
In distributed feedback semiconductor laser devices with a monitor, high doping concentrations in the contact layers lead to reduced depletion layer thickness in the monitor photodetector, causing overcurrent flow and reduced electrostatic discharge (ESD) resistance.
Innovation Solution
The semiconductor laser device includes a photodetector with a main light receiving part and an enlarged part, which increases the outer edge length of the n-type contact layer, thereby reducing current concentration and enhancing ESD withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of the n-type contact layer and p-type contact layer is set to a high concentration to reduce contact resistance, then the contact resistance between the electrode and contact layer is reduced, but the thickness of the depletion layer in the monitor photodetector is reduced, causing overcurrent flow and reduced ESD resistance
Solution Approach 1:
The contact layer structure is segmented into multiple layers with different doping concentrations. The n-type contact layer is divided into a first n-type contact layer (higher doping concentration for low contact resistance) and a second n-type contact layer (lower doping concentration for thicker depletion layer). This segmentation allows each layer to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the contact layer structure are assigned different doping concentrations according to their specific functional requirements. The region closer to the electrode (first n-type contact layer) has higher doping concentration for low contact resistance, while the region closer to the active layer (second n-type contact layer) has lower doping concentration for adequate depletion layer thickness and ESD protection.
2Ease of manufacture
If the doping concentration of the contact layers is high to reduce contact resistance, then electrical connection is improved, but the monitor photodetector experiences overcurrent flow during ESD events
Solution Approach 1:
The contact layer is segmented into multiple layers with different doping concentrations. The first n-type contact layer has higher doping concentration for low contact resistance, while the second n-type contact layer has lower doping concentration for adequate depletion layer thickness and ESD protection.
Solution Approach 2:
The doping concentration parameter is changed across different layers of the contact structure. The first n-type contact layer uses a higher doping concentration (1×10^19 to 1×10^21 atoms/cm³) while the second n-type contact layer uses a lower doping concentration (1×10^17 to 1×10^19 atoms/cm³), optimizing both electrical connection and ESD resistance.
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 increased outer edge length of the n-type contact layer in the photodetector improves the ESD withstand voltage, preventing overcurrent flow and damage to the monitor photodetector.
Implementation Method 1
a photodetector to detect the laser light emitted from the laser part
Implementation Method 2
the thickness of the depletion layer generated in the monitor PD when a voltage is applied to the monitor PD
Data Source
AI summary
The semiconductor laser device comprises a laser part, a waveguide for propagating laser light emitted by the laser part, and a photodetector for detecting the laser light which are formed on the same semiconductor substrate. The photodetector includes a p-type contact layer which is formed above the side of the waveguide on the side opposite to the semiconductor substrate and is connected to an anode electrode, an n-type contact layer connected to a cathode electrode, and an undoped layer formed between the p-type contact layer and the n-type contact layer. The undoped layer and the n-type contact layer in the photodetector include a main light receiving part disposed above the waveguide so as to encompass the waveguide, and an enlarged part disposed so as not to encompass the waveguide while connected to the main light receiving part.