Semiconductor Laser Waveguide Planarity via Segmented Substrate
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Solution Overview
Problem
The challenge is to achieve a semiconductor laser device with a planarized optical waveguide and uniform bandgap energy without controlling the substrate off-angle, as controlling the off-angle increases substrate costs and reduces the number of usable semiconductor laser devices per wafer.
Innovation Solution
The semiconductor laser device is configured with semiconductor layers formed over a stepped region, featuring a strip-shaped optical waveguide in a planar region with periodic surface undulations of smaller variation, which improves planarity and reduces bandgap energy variation, allowing for a single-peaked far-field pattern and enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the off-angle of the substrate is controlled to planarize the optical waveguide, then the planarity of the optical waveguide is improved, but the cost of the substrate increases and the number of usable devices per wafer is reduced
Solution Approach 1:
The substrate surface is segmented into multiple regions with different off-angles. A first region has a first off-angle for forming semiconductor layers with uniform bandgap energy, while a second region has a second off-angle for forming a planar optical waveguide. This segmentation allows different functional requirements to be met in different regions without compromising overall device yield.
Solution Approach 2:
Different regions of the substrate are assigned different local qualities (off-angles) according to their specific functional requirements. The first region uses a specific off-angle optimized for semiconductor layer growth, while the second region uses a different off-angle optimized for waveguide planarity. This local optimization resolves the contradiction between uniform bandgap energy and waveguide planarity without reducing overall productivity.
2Manufacturing precision
If the off-angle of the substrate is controlled to make the bandgap energy uniform, then the uniformity of bandgap energy is improved, but the cost of the substrate increases
Solution Approach 1:
The substrate is divided into regions with different off-angles, where the first region is optimized for uniform bandgap energy formation. This allows the bandgap uniformity requirement to be met locally without requiring the entire substrate to use expensive high-precision off-angle control.
Solution Approach 2:
The first region of the substrate is assigned a specific off-angle quality that ensures uniform bandgap energy, while other regions can use different off-angles. This local quality assignment achieves the desired bandgap uniformity without increasing the cost of the entire substrate.
3Object-affected harmful factors
If surface undulations with periodic structure exist in the optical waveguide, then scattering of laser light occurs, but controlling the off-angle to reduce scattering reduces the number of usable devices per wafer
Solution Approach 1:
The substrate is segmented such that the second region, which forms the optical waveguide, has a specific off-angle that minimizes surface undulations and light scattering. This localized optimization reduces scattering in the critical waveguide region without affecting the usability of other regions on the wafer.
Solution Approach 2:
The second region is assigned a specific off-angle quality that optimizes waveguide planarity and minimizes light scattering. This local quality control addresses the scattering issue in the waveguide region without requiring the entire wafer to be sacrificed, thereby maintaining high productivity.
Data Source
AI summary
A semiconductor laser device includes a semiconductor-layer lamination (20) having an active layer (26) formed over a substrate (11). The semiconductor-layer lamination (20) includes a front face which emits light, a strip-shaped optical waveguide formed in a direction transverse to the front face, a first region (20A) extending in a direction transverse to the front face, a second region (20B) having a top surface whose height is different from that of the first region (20A), and a planar region (20C) formed between the first region (20A) and the second region (20B), and having periodic surface undulations whose variation is smaller than that of the second region (20B). The optical waveguide is formed in the planar region (20C).