Semiconductor Laser Mesa Structure for Precise Resonator End Faces

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Solution Overview

Problem

The formation of resonator end faces in semiconductor laser devices using cleavage results in poor position accuracy due to mechanical variations, which is a significant issue for high-speed DFB lasers, especially in 100 Gbps communication systems, and dry etching, while improving accuracy, faces challenges with ion shadowing and over-etching that increase device resistance and reduce throughput.

Innovation Solution

A semiconductor laser device with a mesa structure and L-shaped grooves formed by dry etching, where the top surface of the contact layer and side faces of the mesa create an L shape, allowing for precise exposure of the contact layer and minimizing thickness, thereby reducing parasitic capacitance and improving position accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If cleavage is used to form resonator end faces, then the manufacturing process is simple, but position accuracy deteriorates due to mechanical variation

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidend face position accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical cleavage process with a dry etching process to form resonator end faces. This substitution eliminates the mechanical variation inherent in cleavage and achieves submicron-level position accuracy through photolithography alignment, directly resolving the contradiction between manufacturing simplicity and position accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If dry etching is used to form resonator end faces and expose contact layer, then position accuracy is improved, but over-etching increases device resistance and reduces throughput

Engineering Contradiction:

Improveend face position accuracyVSAvoidepitaxial growth throughput

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent segments the dry etching process into two distinct stages: first forming the resonator end face with precise photolithography alignment, then separately exposing the contact layer. This segmentation allows each step to be optimized independently, preventing over-etching of the contact layer while maintaining submicron position accuracy for the end face.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary action by forming the resonator end face with precise alignment before proceeding to contact layer exposure. This preliminary positioning ensures that subsequent contact layer processing does not require excessive etching, thereby preserving contact layer thickness and maintaining high epitaxial growth throughput.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If contact layer thickness is increased to compensate for over-etching, then device resistance is reduced, but throughput of epitaxial growth apparatus decreases

Engineering Contradiction:

Improvedevice resistanceVSAvoidepitaxial growth throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the mechanical approach of increasing contact layer thickness to compensate for over-etching with a controlled dry etching process using photolithography alignment. This substitution achieves precise end face positioning without excessive etching, thereby maintaining contact layer thickness and ensuring high epitaxial growth throughput while keeping device resistance low.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The method achieves high position accuracy and reduced parasitic capacitance, enhancing the throughput of the epitaxial growth apparatus and improving the SMSR yield in multi-wavelength integrated semiconductor laser devices.

Implementation Method 1

a first groove and a second groove are formed in an n-type cladding layer by dry etching

Methodology Applied

Scientific EffectDry etching: Plasma

Data Source

PatentUS11870212B2Semiconductor laser device and method for manufacturing the same

Publication Date: 2024.01.09 MITSUBISHI ELECTRIC CORP

AI summary

A mesa (34) includes a resonator and a second conductivity type contact layer (24). Grooves (32) are provided on both sides of the mesa (34). The first conductivity type contact layer (12) and a side face of the mesa (34) including an end face of the resonator construct an L shape (50). The first conductivity type contact layer (12) constructs bottom surfaces of the L shape (50) and the grooves (32). A side face of the groove (32) includes a slope (38) near the bottom surface (46) and a side face (42) above. A side face of the L shape (50) includes a slope (40) near the bottom surface (48) and a side face (44) above. A first electrode (28) is connected to the first conductivity type contact layer (12) at the bottom surface (46) of the groove (32). A second electrode (30) is connected to the second conductivity type contact layer (24) above the mesa (34).