Quantum Cascade Laser Insulating Film Segmentation
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Solution Overview
Problem
The existing quantum cascade lasers face issues with breakdown of insulating films due to high voltage application, leading to device failures and reduced productivity, as well as quality deterioration of the end face caused by thick insulating films and stress.
Innovation Solution
A quantum cascade laser design that includes a second insulating film to isolate the metal film from the solder material, preventing voltage application to the insulating film and enhancing mechanical strength, along with a partly-thinned electrode structure to reduce leakage current and improve cleavage yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick insulating film is formed on the end face to prevent breakdown, then reliability is improved, but manufacturing precision deteriorates due to stress and quality deterioration
Solution Approach 1:
The insulating film structure is segmented into multiple layers: a first insulating film directly on the end face, a metal film on top of it, and a second insulating film covering the metal film. This segmentation allows each layer to perform its specific function - the first insulating film provides base insulation, the metal film provides reflective function, and the second insulating film protects the metal film from solder material, thereby preventing breakdown while maintaining end face quality.
Solution Approach 2:
The second insulating film acts as an intermediary layer between the metal film and the solder material. This intermediary prevents direct contact and potential breakdown caused by voltage application to the metal film, while also protecting the end face quality by preventing stress and deterioration from propagating to the semiconductor layers.
2Power
If high voltage is applied to the laser, then power output is improved, but reliability deteriorates due to insulating film breakdown
Solution Approach 1:
The patent implements beforehand cushioning by forming the second insulating film to cover the metal film before any potential breakdown can occur. This protective layer is prepared in advance to withstand high voltage conditions, preventing voltage from being applied to the metal film and thereby preventing breakdown even when high power is required for laser operation.
3Ease of manufacture
If the electrode is made uniformly thick, then ease of manufacture is improved, but productivity deteriorates due to low cleavage yield
Solution Approach 1:
The electrode structure implements local quality by having different thicknesses in different regions. The first electrode has a first thickness in the laser light emission region and a second thickness (smaller than the first) in the cleavage region. This local variation optimizes each region for its specific function - the thicker region provides good electrical contact for light emission, while the thinner region facilitates clean cleavage, thereby improving productivity without compromising ease of manufacture.
Data Source
AI summary
A quantum cascade laser includes: a semiconductor substrate including principal and back surfaces; a semiconductor laminate having a laminate end face, the laminate end face and, the substrate end face extending along a reference plane intersecting a second direction that intersects the first direction; a first electrode disposed on the semiconductor laminate, the semiconductor laminate being disposed between the first electrode and the semiconductor substrate; a second electrode disposed on the back surface; a first insulating film disposed on the laminate end face, the substrate end face, and the first electrode; a metal film disposed on the first insulating film and the laminate end face, the substrate end face, and the first electrode; and a second insulating film disposed on the second electrode, and on the substrate end face, the metal film being disposed between the first insulating film and the second insulating film.