Quantum Cascade Laser Distributed Bragg Reflection Surface Flatness
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Solution Overview
Problem
The buried heterostructure quantum cascade semiconductor laser with a wide distributed Bragg reflection region suffers from poor surface flatness, leading to non-uniform patterning and reduced processing accuracy, which affects the in-plane uniformity and reproducibility of the distributed Bragg reflection region, resulting in low yield.
Innovation Solution
The quantum cascade semiconductor laser features a substrate with a mesa waveguide and alternating arrays of bulk semiconductor regions and laminate regions, which provide improved surface flatness and uniformity, allowing for precise resist patterning and enhanced processing accuracy of the distributed Bragg reflection region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wide distributed Bragg reflection region is formed in a buried heterostructure quantum cascade semiconductor laser, then the reflectivity and optical performance are improved, but the surface flatness deteriorates leading to poor patterning accuracy
Solution Approach 1:
The distributed Bragg reflection region is segmented into multiple high refractive index portions and low refractive index portions that are alternately arranged. This segmentation allows each portion to be independently formed with precise control over thickness and composition, enabling accurate patterning while achieving the desired wide reflectivity region. The alternating structure divides the complex wide region into manageable repeating units.
Solution Approach 2:
Different portions of the distributed Bragg reflection region are assigned different local qualities through the use of semiconductor layers with different refractive indices. The high refractive index portions and low refractive index portions have distinct optical properties that are optimized for their specific roles in the Bragg reflection mechanism, allowing precise control of optical performance across the wide region while maintaining manufacturing accuracy.
2Strength
If stripe-shaped mesas are buried by regrowth to form a burying region, then the mechanical strength is improved, but the surface flatness deteriorates due to thickness variation in the burying region
Solution Approach 1:
The semiconductor layers are formed with predetermined thicknesses and refractive index profiles before the burying regrowth process. By pre-configuring the alternating high and low refractive index portions with controlled thicknesses, the patent ensures that the subsequent burying region formation does not compromise surface flatness. The preliminary structuring allows the burying region to be formed uniformly across the wafer surface.
3Manufacturing precision
If optimal exposure conditions are applied for resist patterning, then the patterning precision is improved, but the uniformity across the wafer deteriorates due to depression in the burying region
Solution Approach 1:
The patent controls the thickness parameters of the alternating semiconductor layers to create a surface profile that compensates for the depression in the burying region. By adjusting the thickness of high and low refractive index portions, the overall surface flatness is maintained at a level that allows uniform exposure conditions to be applied across the entire wafer, ensuring both precise patterning and in-plane uniformity.
Data Source
AI summary
A quantum cascade semiconductor laser includes a substrate with a main surface including a waveguide area and a distributed Bragg reflection area that are arranged in a direction of a first axis; a laser region provided on the waveguide area, the laser region including a mesa waveguide having first and second side surfaces, and first and second burying regions provided on the first and second side surfaces, respectively; a distributed Bragg reflection region provided on the distributed Bragg reflection area, the distributed Bragg reflection region including a semiconductor wall having first bulk semiconductor regions and first laminate regions that are alternately arrayed in a direction of a second axis intersecting the first axis; and an upper electrode provided on the laser region. Each first bulk semiconductor region includes a bulk semiconductor layer. Each first laminate region includes a stacked semiconductor layer having a plurality of semiconductor layers.