Ridge Laser Element Structure for Lateral Current Suppression
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Solution Overview
Problem
In nitride semiconductor laser elements, increasing the width of the ridge to enhance current supply leads to excessive current flow through the lateral surface, resulting in non-radiative recombination, heat generation, and crystal defects, which reduce output and reliability.
Innovation Solution
A laser element design featuring a p-type semiconductor layer with a ridge structure, where a stepped portion is formed in the contact layer at the boundary between the lateral and principal surfaces, reducing current flow through the lateral surface by creating regions with different Mg concentrations to control contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the width of the ridge is increased to enhance current supply, then the current supply capability is improved, but excessive current flows through the lateral surface causing non-radiative recombination and heat generation
Solution Approach 1:
The patent applies local quality by creating a stepped portion only at the boundary region between the lateral surface and principal surface of the ridge, rather than uniformly modifying the entire ridge structure. This localized modification introduces different Mg concentrations specifically where current leakage occurs, suppressing non-radiative recombination at the critical boundary region while maintaining the overall ridge width for adequate current supply capability
Solution Approach 2:
The patent changes the compositional parameter (Mg concentration) in the contact layer by forming a stepped portion with different Mg concentrations. The first Mg concentration in the stepped portion is higher than the second Mg concentration, creating a gradient that controls contact resistance and suppresses current flow through the lateral surface, thereby reducing non-radiative recombination loss while maintaining productivity
2Productivity
If the width of the ridge is increased to enhance current supply, then the current supply capability is improved, but heat generation increases due to non-radiative recombination
Solution Approach 1:
The stepped portion is localized at the boundary region where current leakage and subsequent heat generation occur. By concentrating the Mg concentration gradient specifically at this boundary region rather than throughout the entire ridge, the patent suppresses non-radiative recombination at the heat-generating interface while maintaining adequate current supply capability through the ridge's overall width
Solution Approach 2:
The patent converts the potentially harmful high current flow through the lateral surface into a controlled current path by using the stepped portion with graded Mg concentrations. The higher Mg concentration region acts as a barrier that redirects current flow away from the lateral surface, transforming what would be a harmful current leakage path into a controlled current distribution that reduces heat generation while maintaining productivity
3Productivity
If the width of the ridge is increased to enhance current supply, then the current supply capability is improved, but crystal defects increase near the lateral surface
Solution Approach 1:
The stepped portion with graded Mg concentrations is formed specifically at the boundary region between the lateral surface and principal surface, where crystal defects tend to form. This localized compositional modification suppresses defect formation at the critical boundary region while maintaining the overall ridge width for adequate current supply capability
Solution Approach 2:
The stepped portion with higher Mg concentration acts as a preventive barrier formed beforehand at the boundary region where crystal defects are likely to occur. This prior cushioning structure prevents defect formation by controlling the current distribution and reducing non-radiative recombination at the vulnerable boundary region, thereby improving reliability while maintaining productivity
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 design enhances drive efficiency and reliability by suppressing current flow through the lateral surface, reducing non-radiative recombination and crystal defects, thereby increasing output and extending the laser element's operational lifespan.
Implementation Method 1
a stepped portion defined by recessing the contact layer is formed in at least part of a boundary between a lateral surface among surfaces defining outer edges of the ridge, the lateral surface extending along a lengthwise direction of the ridge, and the principal surface of the ridge
Data Source
AI summary
A laser element comprises a substrate; and an n-type semiconductor layer, a light emitting layer, a p-type semiconductor layer, and an electrode layer successively laminated on one principal surface of the substrate, wherein the p-type semiconductor layer includes a ridge raised in a stripe shape, the ridge including a contact layer formed in a layer including a principal surface on a side opposite to the substrate, a stepped portion defined by recessing the contact layer is formed in at least part of a boundary between a lateral surface among surfaces defining outer edges of the ridge, the lateral surface extending along a lengthwise direction of the ridge, and the principal surface of the ridge, and the electrode layer covers the principal surface of the ridge and the stepped portion.