Near-Infrared Quantum Cascade Laser with AlGaN Superlattice
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lasing operation in the near-infrared wavelength range has not been achieved with quantum cascade lasers due to the large photon energy requiring significant conduction band offsets, which is technically challenging with existing GaN/AlGaN-based materials.
Innovation Solution
A quantum cascade laser element with a semiconductor superlattice structure comprising four well layers of AlxGa1-xN separated by barrier layers of AlyGa1-yN, where the maximum thickness well layer accommodates only two confinement levels, allowing for near-infrared emission under an external voltage, and an index guide structure is used to enhance electron injection and optical gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If GaN/AlGaN-based materials are used to achieve large conduction band offset for near-infrared emission, then the photon energy requirement is met, but the manufacturing complexity and difficulty increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the aluminum composition ratios (x and y) in AlxGa1-xN well layers and AlyGa1-yN barrier layers to optimize the conduction band offset. By changing these compositional parameters, the patent achieves the required large offset for near-infrared emission while maintaining manufacturability through controlled material synthesis
Solution Approach 2:
The patent employs composite materials by creating a superlattice structure composed of alternating AlxGa1-xN well layers and AlyGa1-yN barrier layers. This composite structure combines materials with different band offsets to achieve the desired electronic and optical properties for near-infrared lasing while managing the manufacturing challenges through systematic material design
2Ease of manufacture
If the conduction band offset is increased to enable near-infrared lasing, then the emission wavelength is achieved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the active region into multiple thin quantum well layers (four GaN layers) separated by barrier layers. This segmented superlattice structure allows each layer to be optimized independently for specific functions (carrier confinement, optical transition) while collectively achieving the near-infrared emission wavelength, thereby managing device complexity through modular design
Solution Approach 2:
The patent transitions to another dimension by utilizing the quantum confinement effect in the thickness direction of the superlattice structure. By controlling the thickness of well and barrier layers in the growth direction, the patent achieves precise control over energy levels and emission wavelength without increasing lateral complexity, effectively solving the wavelength achievement problem through dimensional optimization
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 design enables practical lasing operation in the near-infrared wavelength range with high optical gain and efficient electron injection, overcoming the limitations of previous technologies by adjusting the barrier height and wavelength range using GaN/AlGaN-based materials.
Implementation Method 1
The carriers, which are electrons, transport through the sub-bands which formed in the tilted and irregular potential, and undergo repeated inter-subband transitions (ISBT). The electrons are coupled with the electromagnetic field at each transition to produce stimulated emission and induce laser oscillation (lasing).
Implementation Method 2
The electrons are coupled with the electromagnetic field at each transition to produce stimulated emission and induce laser oscillation (lasing).
Implementation Method 3
The potential acting on electrons generally has multiple wells and barriers in each unit structure. The wells and barriers of the potential for electrons are determined by the material of each layer of the unit structure, creating irregularities that reflect the conduction band offset according to position in the thickness
Implementation Method 4
an index guide structure is used to enhance electron injection and optical gain
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
In order to provide a QCL element operating in the near-infrared wavelength range, the present disclosure provides a quantum cascade laser element 1000 having a semiconductor superlattice structure (QCL structure 100) sandwiched between a pair of conductive sections 20 and 30. The semiconductor superlattice structure serves as an active region that emits electromagnetic waves of a certain wavelength in the near-infrared range under an external voltage applied through the pair of conductive sections for operation. The active region has a plurality of unit structures 10U that are repeatedly stacked. Each unit structure consists of four well layers 10W1-10W4 of a composition of AlxGa1-xN, separated from each other by barrier layers 10B1-10B5 of a composition of AlyGa1-yN with 0≤x<y≤1. One of these well layers is the maximum thickness well layer, thicker than the others. Both of the pairs of conductive sections have a refractive index lower than that of the active region in which doped TCO inserted as a key role.