Light-Emitting Element With Elevated Electrode Wall Structure
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Solution Overview
Problem
In surface-emitting laser elements, a large displacement between the current constriction region and the p-type electrode can occur due to misalignment and variations in oxidation rates, leading to light being blocked by the electrode, resulting in optical output loss and defects in the far-field pattern.
Innovation Solution
A light-emitting element with a mesa structure featuring a current constriction region surrounded by an insulation region, connected via a bridge structure and wall structure, with the second electrode placed on the wall structure to prevent light blocking, allowing for reliable light emission even with significant displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the p-side electrode is positioned close to the current constriction region to improve current injection efficiency, then current injection efficiency is improved, but light from the active layer is blocked by the electrode causing optical output loss and far-field pattern defects
Solution Approach 1:
The patent introduces a vertical dimension by forming the p-side electrode on a raised portion (protrusion or wall structure) that extends upward from the mesa structure. This elevates the electrode in the vertical direction, moving it out of the horizontal light propagation path while maintaining its electrical connection function. The electrode remains positioned to provide effective current injection into the active layer through the raised structure, but light traveling horizontally through the cavity is no longer blocked by it.
2Area of stationary object
If the mesa structure size is reduced to improve device integration and reduce capacitance, then device integration is improved and capacitance is reduced, but the alignment tolerance for the p-side electrode and current constriction region is reduced making displacement more critical
Solution Approach 1:
By raising the p-side electrode on a vertical protrusion or wall structure, the patent creates a three-dimensional configuration where the electrode's horizontal position can be optimized for electrical connection while its vertical elevation prevents light blocking. This dimensional transition provides design flexibility that decouples the alignment requirements, allowing smaller mesa structures without proportionally tighter alignment tolerances.
Solution Approach 2:
The raised portion (protrusion or wall structure) acts as an intermediary element between the p-side electrode and the mesa structure base. This intermediate structure provides both mechanical support and positional adjustment, allowing the electrode to be positioned optimally for current injection while maintaining sufficient distance from the light path. The intermediary structure absorbs some of the alignment sensitivity.
3Reliability
If oxidation treatment is performed to form the current constriction region, then current constriction is achieved, but displacement between the current constriction region and p-side electrode occurs due to variations in oxidation rates
Solution Approach 1:
The patent resolves the alignment sensitivity issue by transitioning to a vertical configuration where the p-side electrode is positioned on a raised portion. This vertical arrangement allows the electrode to be positioned at a height where it effectively contacts the current constriction region formed by oxidation, while variations in oxidation depth or horizontal position have reduced impact on the overall alignment. The vertical dimension provides a buffer against lateral displacement errors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures that light from the active layer is not blocked by the p-side electrode, maintaining optical output and preventing defects in the far-field pattern, while allowing for reduced size of mesa structures and current constriction regions.
Implementation Method 1
By oxidizing a part of the p-type compound semiconductor layer from the sidewall portion of the mesa structure, a current constriction region is provided in the center of the p-type compound semiconductor layer
Data Source
AI summary
A light-emitting element includes a mesa structure in which a first compound semiconductor layer of a first conductivity type, an active layer, and a second compound semiconductor layer of a second conductivity type are disposed in that order, wherein at least one of the first compound semiconductor layer and the second compound semiconductor layer has a current constriction region surrounded by an insulation region extending inward from a sidewall portion of the mesa structure; a wall structure disposed so as to surround the mesa structure; at least one bridge structure connecting the mesa structure and the wall structure, the wall structure and the bridge structure each having the same layer structure as the portion of the mesa structure in which the insulation region is provided; a first electrode; and a second electrode disposed on a top face of the wall structure.