Tensile Strained InAlAs Electron Blocker for 1310nm Laser
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Solution Overview
Problem
High-temperature operation of semiconductor lasers, particularly those emitting at wavelengths below 1310 nm, faces inefficiencies due to n-type carrier diffusion into p-doped cladding, leading to non-radiative recombination and reduced optical power, despite lattice-matched InAlAs layers which do not fully prevent carrier leakage.
Innovation Solution
Incorporating a thin layer of tensile strained InAlAs as an electron blocker between the Multiple-Quantum-Wells and the p-doped InP cladding, enhancing the conduction band energy discontinuity to prevent carrier diffusion, which can be further improved with increased p-type doping of the InAlAs layer without significant optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lattice-matched InAlAs layer is inserted to prevent carrier diffusion, then carrier confinement is improved, but carrier leakage still occurs at high temperatures above 80°C
Solution Approach 1:
The patent introduces tensile strain as a new parameter to modify the InAlAs layer properties. By applying tensile strain (e.g., through lattice mismatch with InP substrate or compositional adjustment), the conduction band edge is lowered, enhancing the electron blocking effect. This parameter change allows the same material layer to provide superior carrier confinement at high temperatures compared to the relaxed or lattice-matched state.
Solution Approach 2:
The patent creates a composite structure by combining strained InAlAs with the existing InGaAlAs/InP laser structure. The strained InAlAs layer forms a composite electron blocking barrier that leverages both the high bandgap of InAlAs and the strain-induced band structure modification, achieving synergistic carrier confinement that prevents leakage at elevated temperatures.
2Reliability
If p-type doping is increased in the InAlAs layer to improve electron blocking, then carrier confinement is enhanced, but optical losses may increase
Solution Approach 1:
The patent applies local quality by creating a spatially non-uniform doping profile within the InAlAs layer. The p-type doping is concentrated specifically at the interface with the InGaAlAs layer where electron blocking is most critical, while other regions maintain lower doping to preserve optical transparency. This localized doping strategy enhances electron blocking efficiency without proportionally increasing optical losses throughout the entire layer.
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 significantly improves optical power and wall plug efficiency by reducing carrier leakage, with a 43% increase in peak wall plug efficiency and 60% increase in optical power at fixed current, while maintaining diode characteristic voltage, effectively addressing the inefficiencies at high temperatures.
Implementation Method 1
enhancing the conduction band energy discontinuity to prevent carrier diffusion
Implementation Method 2
n-type carriers (electrons) tend to overflow the confinement barrier formed by the p-doped cladding, and then diffuse into the p-doped cladding
Implementation Method 3
Incorporating a thin layer of tensile strained InAlAs as an electron blocker
Implementation Method 4
which can be further improved with increased p-type doping of the InAlAs layer
Data Source
AI summary
Embodiments may relate to a multiple quantum well (MQW) laser for operating at high temperatures, comprising at least one quantum well made of compressively strained InGaAlAs layers that are alternatively stacked with tensile strained InGaAlAs layers, the at least one quantum well surrounded on one side by a n-doped InP cladding and on the other by a p-doped InP cladding so as to form a double hetero-junction. A confinement layer of lattice-matched InAlAs may be provided between the quantum well and the p-doped cladding, having a first surface facing or adjacent to the quantum well and a second surface facing or adjacent to the p-doped cladding. An additional electron containment layer of tensile strained InAlAs may be provided facing or adjacent to one surface of the confinement layer, having a thickness smaller than that of the confinement layer. Other embodiments may be described and/or claimed.