Optical Semiconductor Device Butt Joint Reliability
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Solution Overview
Problem
Conventional monolithic integration of semiconductor lasers and waveguides in optical semiconductor devices leads to light scattering, mode conversion losses, crystal defects, and current concentration at the butt joint interface due to lattice mismatch and energy band differences, resulting in reliability issues.
Innovation Solution
Incorporating an undoped InP middle layer with a band gap greater than the waveguide layer, positioned between the active layer and the waveguide layer but not on the active layer, to suppress electron flow into the waveguide layer and prevent hole injection inhibition, thereby reducing current concentration at the butt joint interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a p-type InP middle layer is inserted in the butt joint interface, then light scattering and mode conversion losses are suppressed, but hole injection into the active layer is inhibited due to band notch, causing current concentration in the butt joint interface
Solution Approach 1:
An undoped InP middle layer is introduced as an intermediary between the active layer and waveguide layer. This middle layer has a band structure that is intermediate between the n-type cladding layer and the waveguide layer, allowing electrons to pass through while blocking holes from the waveguide layer, thus preventing current concentration without forming a band notch that would inhibit hole injection into the active layer.
Solution Approach 2:
The middle layer is positioned only in the region where it is needed - between the n-type cladding layer and the waveguide layer - while deliberately not covering the active layer. This localized placement allows the middle layer to suppress electron flow into the waveguide layer without interfering with hole injection into the active layer, thus avoiding current concentration issues.
2Productivity
If butt joint growth is used to integrate numerous devices, then monolithic integration is achieved, but crystal defects are generated due to contamination and crystal lattice mismatch, causing current concentration and heat stress
Solution Approach 1:
The undoped InP middle layer serves as a buffer intermediary between layers with different crystal structures and energy bands. It reduces the impact of crystal lattice mismatch and contamination at the butt joint interface, suppressing current concentration caused by these defects while maintaining the monolithic integration capability.
3Loss of energy
If the middle layer is provided on the active layer, then electron flow into the waveguide layer is suppressed, but hole injection into the active layer is inhibited, increasing current density in the butt joint interface
Solution Approach 1:
The middle layer is strategically positioned only in the region between the n-type cladding layer and the waveguide layer, deliberately excluding the active layer area. This localized placement creates a spatial differentiation where the middle layer suppresses electron flow into the waveguide layer in its region, while leaving the active layer region unaffected, thus allowing normal hole injection without current concentration.
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 configuration effectively reduces current concentration and enhances the reliability of the optical semiconductor device by minimizing crystal defects and leak currents, improving the integration process and device performance.
Implementation Method 1
a middle layer provided between the side of the active layer and the side of the waveguide layer, provided between the n-type cladding layer and the waveguide layer, not provided on the active layer, and having a band gap greater than a band gap of the waveguide layer
Data Source
AI summary
An optical semiconductor device includes: an n-type semiconductor substrate; an n-type cladding layer provided on the n-type semiconductor substrate; an active layer of a semiconductor laser provided on the n-type cladding layer; a waveguide layer of a waveguide provided on the n-type cladding layer and having a side facing a side of the active layer; a p-type cladding layer provided on the active layer and the waveguide layer; and a middle layer provided between the side of the active layer and the side of the waveguide layer, provided between the n-type cladding layer and the waveguide layer, not provided on the active layer, and having a band gap greater than a band gap of the waveguide layer.