Edge-Emitting Laser Diode Window Region Leak Current Suppression
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Solution Overview
Problem
The technical challenge lies in suppressing leak current in the window region of edge-emitting lasers with a ridge-waveguide structure, particularly for short cavity type lasers, which affects low-current operation and laser characteristics, as conventional methods fail to completely eliminate leak current due to interdiffusion issues with dopants like Fe and Zn.
Innovation Solution
The introduction of Ru-doped semi-insulating layers in the window region, either alone or in combination with Fe-doped layers, to increase resistivity and reduce leak current, with Ru providing higher resistivity without interdiffusion with Zn, and Fe-doped layers enhancing the suppression effect by reducing p-type doping concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Fe-doped semi-insulating layers are used in the window region, then resistivity increases and leak current is suppressed, but interdiffusion between Fe and Zn dopants reduces the effectiveness of leak current suppression
Solution Approach 1:
The patent introduces an undoped InP layer as an intermediary barrier between the Fe-doped semi-insulating layer and the Zn-doped p-type cladding layer. This intermediary layer prevents direct interdiffusion between Fe and Zn dopants, maintaining the stability of both doping concentrations while preserving the high resistivity needed for leak current suppression.
Solution Approach 2:
The window region structure is segmented into multiple distinct layers: Fe-doped semi-insulating layer, undoped InP barrier layer, and Zn-doped p-type cladding layer. This segmentation physically separates the dopant sources and prevents their interdiffusion, allowing each layer to maintain its intended electrical properties independently.
2Use of energy by moving object
If the cavity length is shortened to reduce drive current and power consumption, then low-current operation is achieved, but leak current in the window region becomes more significant and degrades laser characteristics
Solution Approach 1:
The patent changes the electrical parameters of the window region by introducing Fe-doped semi-insulating layers with very high resistivity (greater than 10^7 Ωcm). This parameter change in the window region's resistivity effectively suppresses leak current, allowing the laser to maintain good characteristics even with short cavity length and low drive current operation.
3Reliability
If Ru-doped semi-insulating layers are used instead of Fe-doped layers, then higher resistivity is achieved without interdiffusion issues, but manufacturing complexity may increase
Solution Approach 1:
The patent changes the dopant material from Fe to Ru, which provides even higher resistivity in the semi-insulating layer. Ru doping achieves superior leak current suppression without the interdiffusion problem that plagues Fe-doped structures, though it may require adjusted manufacturing parameters for optimal results.
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 approach significantly reduces leak current, enabling low-current operation and improving laser reliability and manufacturing yield by increasing the resistivity of the window region, effectively addressing the issue of leak current in short cavity type lasers.
Implementation Method 1
Ru providing higher resistivity without interdiffusion with Zn
Implementation Method 2
Fe-doped layers enhancing the suppression effect by reducing p-type doping concentration
Data Source
AI summary
In an edge emitting laser having a window region with a ridge-waveguide structure, particularly, in a short cavity type of a laser operated with a low current, there has been a problem of its operating current being increased due to current leakage of the window portion. To solve this problem, in the window region, between an n-type substrate and a p-type cladding layer, a semi-insulating semiconductor layer into which Ru is doped is inserted. Alternatively, a stacked structure of a Ru-doped layer and a Fe-doped layer is introduced.