Semiconductor Laser Element Current Injection Prevention Layer
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Solution Overview
Problem
Semiconductor laser elements connected in series often become discontinuous due to local current concentration and pn junction deterioration, leading to failure and cessation of light emission, as individual elements stop functioning when one becomes unlit.
Innovation Solution
A semiconductor laser element design featuring a semiconductor stack with a ridge, a first electrode layer, a current injection prevention layer with island or protrusion portions to reduce current injection into high-risk regions, and a second electrode layer to maintain efficient operation by preventing physical failure and discontinuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrode structure is used, then current injection is efficient, but local current concentration occurs causing pn junction deterioration and discontinuity
Solution Approach 1:
The patent applies local quality by creating a current injection prevention layer with varying thickness across different regions. The layer has greater thickness (higher prevention capability) in regions prone to current concentration and smaller thickness (lower prevention capability) in regions requiring current injection, thereby locally optimizing current distribution to prevent discontinuity while maintaining efficient operation.
Solution Approach 2:
The current injection prevention layer is formed in advance on the ridge before final electrode configuration. This preliminary structure proactively prevents current from concentrating in vulnerable regions before damage can occur, addressing the reliability issue before it manifests as actual discontinuity or failure.
2Reliability
If current injection prevention layer covers entire ridge, then discontinuity is prevented, but power conversion efficiency decreases
Solution Approach 1:
The current injection prevention layer is designed with spatially varying thickness rather than uniform coverage. By making the layer thinner in regions where current injection is needed and thicker in regions where prevention is needed, the patent achieves both reliability improvement and energy efficiency, avoiding the trade-off that would result from complete coverage.
Solution Approach 2:
Instead of applying full coverage of the prevention layer across the entire ridge, the patent uses partial coverage with controlled thickness variation. This partial action approach provides sufficient prevention where needed while allowing adequate current injection where required, optimizing both reliability and efficiency.
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
A semiconductor laser element includes: a semiconductor stack with a ridge, the semiconductor stack having an emission surface and a reflection surface; a first electrode layer extending in the lengthwise direction and disposed on the ridge in contact with the semiconductor stack; a current injection prevention layer covering at least a part of an upper surface from side surfaces of the first electrode layer, and being in contact with the first electrode layer at 18 to 80% of a contact surface area between the first electrode layer and the semiconductor stack; and a second electrode layer disposed on the current injection prevention layer, and being in contact with a part of the first electrode layer, edges of the second electrode layer being disposed closer to the emission surface and the reflection surface than edges of the first electrode layer, respectively..