Capacitance Reducing Region in P-Type Quantum Dot Laser Ridge
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Solution Overview
Problem
Conventional p-type quantum dot laser devices face challenges in maintaining low electrostatic capacitance while operating in a single transverse mode, as narrowing the upper cladding layer to reduce capacitance increases device resistance and can lead to higher harmonic transverse mode oscillation.
Innovation Solution
The optical semiconductor device incorporates a capacitance reducing region with a higher resistivity or opposite conductivity type to the ridge portion, extending at least to the lower surface of the cover portion, which restricts the pn junction interface and reduces electrostatic capacitance, while maintaining a wider ridge portion to prevent higher harmonic transverse mode oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the upper cladding layer is made narrow to reduce electrostatic capacitance, then the electrostatic capacitance decreases, but the device resistance increases
Solution Approach 1:
The patent applies local quality by creating a capacitance reducing region with different conductivity properties (higher resistivity or opposite conductivity type) specifically in the regions adjacent to the ridge portion, while maintaining the ridge portion's original conductivity. This allows the narrow ridge to maintain low resistance while the adjacent regions contribute to capacitance reduction.
2Shape
If the upper cladding layer is made narrow to reduce electrostatic capacitance, then the electrostatic capacitance decreases, but higher harmonic transverse mode oscillation occurs
Solution Approach 1:
The patent creates a capacitance reducing region with specific conductivity properties in localized areas adjacent to the ridge portion. This local modification allows the ridge to remain narrow enough to suppress higher harmonic transverse modes while the capacitance reducing region provides additional electrical isolation to further reduce capacitance without compromising mode stability.
3Shape
If the pn junction interface is restricted to reduce electrostatic capacitance, then the electrostatic capacitance decreases, but device resistance increases
Solution Approach 1:
The patent creates a capacitance reducing region with higher resistivity or opposite conductivity type adjacent to the ridge portion. This region acts as an electrical isolator that further reduces capacitance by minimizing charge storage in the junction interface, while the ridge portion itself maintains low resistance through its optimized conductivity and dimensions.
Data Source
AI summary
An active layer having a p-type quantum dot structure is disposed over a lower cladding layer made of semiconductor material of a first conductivity type. An upper cladding layer is disposed over the active layer. The upper cladding layer is made of semiconductor material, and includes a ridge portion and a cover portion. The ridge portion extends in one direction, and the cover portion covers the surface on both sides of the ridge portion. A capacitance reducing region is disposed on both sides of the ridge portion and reaching at least the lower surface of the cover portion. The capacitance reducing region has the first conductivity type or a higher resistivity than that of the ridge portion, and the ridge portion has a second conductivity type. If the lower cladding layer is an n-type, the capacitance reducing region reaches at least the upper surface of the lower cladding layer.