Ridge Waveguide Semiconductor Laser ITO Layout for Crack-Free Cleavage
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Solution Overview
Problem
Existing semiconductor laser elements face reliability issues due to the generation of steps or cracks during wafer cleavage, which can deteriorate laser characteristics and reduce reliability.
Innovation Solution
A semiconductor laser element design that includes band-shaped ITO side bands extending towards both end surfaces, with regions between these side bands cut into a rectangular shape and in contact with the end surfaces, and an insulating layer covering these regions, to suppress the generation of steps and cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If RIE is performed on laminated layers of ITO and p-type GaN to form a ridge, then the ridge can be formed with perpendicular side surfaces, but stress concentration occurs at the root portion of the ridge during wafer cleavage
Solution Approach 1:
The patent applies curvature by forming a curved surface at the root portion of the ridge through selective etching. This curved transition replaces the sharp perpendicular corner with a gradual curve, distributing stress more evenly and preventing stress concentration during wafer cleavage while maintaining the perpendicular side surfaces for optical performance
2Reliability
If the ridge is formed by RIE on ITO and p-type GaN layers, then electrical connection is established, but steps or cracks are generated on end surfaces during cleavage
Solution Approach 1:
The patent extracts or removes the ITO layer specifically from the ridge root portion through selective etching. By removing the ITO layer at the critical stress concentration point, the rigid structure that causes step generation during cleavage is eliminated, allowing the wafer to cleave smoothly without generating steps or cracks on the end surfaces
3Reliability
If ITO is used as the anode electrode, then light transmittance is high and electrical conductivity is good, but the ITO layer is disposed in the vicinity of the active layer causing potential reliability issues
Solution Approach 1:
The patent removes the ITO layer from the ridge root portion where it causes harm during cleavage, while preserving it in other regions where it provides beneficial electrical conductivity and light transmittance. This selective extraction eliminates the harmful stress concentration effect while maintaining the useful electrical and optical properties of the ITO electrode
Data Source
AI summary
Provided is a semiconductor laser element in which a step or edge crack is suppressed from being generated in an ITO layer or a semiconductor portion in contact with the ITO layer on a front end surface or a rear end surface during cleavage of a wafer in a ridge waveguide type end surface emission laser to improve reliability and yield. The configuration includes a GaN substrate, a nitride semiconductor layer of a first conductivity type laminated on the GaN substrate, an active layer laminated on the nitride semiconductor layer of the first conductivity type, a nitride semiconductor layer of a second conductivity type laminated on the active layer and formed in a ridge waveguide structure, transparent conductive film side bands laminated on the nitride semiconductor layer of the second conductivity type and extending in a band shape along a longitudinal direction toward both end surfaces, a transparent conductive film provided continuously with the transparent conductive film side bands, laminated on the nitride semiconductor layer of the second conductivity type, and formed with each of regions sandwiched between the transparent conductive film side bands and cut in a rectangular shape to be in contact with the end surfaces, an insulating layer laminated on the transparent conductive film, and a metal layer laminated on the insulating layer.