VCSEL Protrusion Sidewall Structure for Stable P-Electrode Current Injection
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Solution Overview
Problem
In vertical cavity surface emitting lasers with a protrusion on the p-side semiconductor layer, the electrode thickness varies due to the protrusion, leading to increased sheet resistance and current concentration, which can cause electrode breakage.
Innovation Solution
A vertical cavity surface emitting laser element with a protrusion on the p-side semiconductor layer, where the height of the protrusion is smaller than the thickness of the p-electrode, and the lateral surface of the protrusion is inclined at an angle less than 60 degrees, reducing current concentration and electrode thickness variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protrusion is formed on the p-side semiconductor layer for current confinement, then current confinement is improved, but electrode thickness varies and sheet resistance increases
Solution Approach 1:
The patent applies preliminary anti-action by forming an inclined surface on the protrusion before depositing the electrode. This pre-shaped surface prevents the electrode thickness from becoming too thin at the edges, counteracting the thickness variation problem before it occurs during electrode formation.
Solution Approach 2:
The patent changes the geometric parameters of the protrusion by forming an inclined surface with a specific angle (30-60 degrees) rather than a vertical wall. This parameter change allows the electrode to be deposited at a controlled angle, maintaining sufficient thickness while still providing current confinement functionality.
2Reliability
If the electrode extends over the lateral surface of the protrusion, then current path is provided, but sheet resistance increases due to thin film portion
Solution Approach 1:
The inclined surface is formed preliminarily to prevent the electrode from becoming too thin when deposited over the protrusion lateral surface. This pre-shaping ensures that even as the electrode extends to provide current path continuity, the thickness remains controlled and sheet resistance is minimized.
3Reliability
If the electrode has a bent shape due to protrusion undulation, then current path is formed, but current concentration occurs and electrode breakage may occur
Solution Approach 1:
The inclined surface is formed in advance to prevent excessive bending of the electrode. By controlling the angle of the protrusion surface, the electrode experiences reduced curvature and less stress concentration, preventing breakage while still allowing the electrode to conform to the protrusion shape for current path formation.
Solution Approach 2:
The patent changes the geometric parameter of the protrusion surface by using an inclined angle of 30-60 degrees instead of a vertical or highly curved surface. This parameter change reduces the bending stress on the electrode, preventing current concentration and electrode breakage while maintaining current path functionality.
Data Source
AI summary
A vertical cavity surface emitting laser element includes a first light reflecting film, a nitride semiconductor layered body, a p-electrode and a second light reflecting film. The nitride semiconductor layered body includes an n-side semiconductor layer disposed on the first light reflecting film, an active layer disposed on the n-side semiconductor layer, and a p-side semiconductor layer disposed on the active layer. The p-side semiconductor layer includes a protrusion and a surface around the protrusion. The p-electrode is in contact with an upper surface of the protrusion, and extends to the surface around the protrusion. The p-electrode is light-transmissive. The second light reflecting film is disposed on the p-electrode. A height of the protrusion as measured from the surface around the protrusion is smaller than a thickness of the p-electrode.