Mesa Electrode Layout for Optical Semiconductor Heat and Stress

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Solution Overview

Problem

The existing optical semiconductor devices with a gold electrode face challenges in achieving designed characteristics due to stress applied to the semiconductor layer from gold's large thermal expansion coefficient, which also degrades heat dissipation properties.

Innovation Solution

The optical semiconductor device incorporates a three-layer electrode structure of titanium, platinum, and gold, where gold is thicker, but the electrode is arranged such that the second electrode layer is spaced apart from the mesa structure region, reducing stress and improving heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a thick gold electrode layer is arranged continuously from the mesa structure region to the adjacent region, then heat dissipation property is improved, but stress applied to the semiconductor layer increases

Engineering Contradiction:

Improveheat dissipation propertyVSAvoidstress applied to semiconductor layer

Core Design Contradiction:

TemperatureVSStress or pressure

Solution Approach 1:

The second electrode layer (gold layer) is divided into two separate parts: a first part arranged in the mesa structure region and a second part arranged in the adjacent region. These two parts are spaced apart from each other, preventing continuous contact of the thick gold layer with the semiconductor layer while maintaining heat dissipation pathways through both regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure is designed with different configurations in different regions: the first electrode layer (titanium) is arranged continuously from the mesa structure region to the adjacent region for uniform coverage, while the second electrode layer (gold) is arranged discontinuously with spaced parts to locally reduce stress in the mesa region while maintaining heat dissipation capability.

Inventive Principle:

Principle #3Local quality

2Stress or pressure

If gold is arranged only in the upper portion of the mesa structure portion, then stress applied to the semiconductor layer is reduced, but heat dissipation property is degraded

Engineering Contradiction:

Improvestress applied to semiconductor layerVSAvoidheat dissipation property

Core Design Contradiction:

Stress or pressureVSTemperature

Solution Approach 1:

The second electrode layer is segmented into two parts spaced apart, with the second part extending into the adjacent region. This segmentation allows the gold layer to maintain stress-reducing configuration over the mesa structure while simultaneously providing heat dissipation pathways in the adjacent region through the second part.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the electrode is arranged to cover the upper surface and side surface of the mesa structure, then electrical conductivity and heat dissipation are improved, but stress on the optical waveguide region increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidstress on optical waveguide region

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The first electrode layer (titanium) provides continuous coverage from the mesa structure region to the adjacent region for uniform electrical conductivity, while the second electrode layer (gold) is arranged discontinuously with spaced parts to locally reduce stress in the mesa structure region where the optical waveguide is located, while maintaining overall electrical functionality.

Inventive Principle:

Principle #3Local quality

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 achieves a high heat dissipation property while maintaining a low stress property, thereby enhancing the overall performance of the optical semiconductor device.

Implementation Method 1

The electrode being a metal and the optical waveguide region formed of a semiconductor crystal have different thermal expansion coefficients. In particular, gold has a large thermal expansion coefficient, and applies a stress to the optical waveguide because of its thickness.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The electrode is in contact with a semiconductor layer in an upper portion of a ridge portion (mesa structure portion). The electrode has not only a function of driving the optical semiconductor device, but also a function of releasing heat generated in the vicinity of an optical waveguide region in the semiconductor layer to the outside, which leads to an improvement in characteristics.

Methodology Applied

Scientific EffectHeat dissipation: Conduction (thermal)

Data Source

PatentUS20250149857A1Optical semiconductor device

Publication Date: 2025.05.08 WELLS FARGO BANK NA

AI summary

An optical semiconductor device, excellent in a high heat dissipation property and a low stress property, includes: a cladding layer in which a mesa structure portion extending in a first direction is formed; an upper surface electrode including a first electrode layer and a second electrode layer thicker than the first electrode layer; a mesa structure region in which the mesa structure portion is formed; and a first adjacent region adjacent to the mesa structure portion in a second direction perpendicular to the first direction in plan view. The first electrode layer is arranged continuously from the mesa structure region to the first adjacent region. The second electrode layer includes a first part arranged in the mesa structure region, and a second part arranged in the first adjacent region. The second part has a part spaced apart from the first part in the second direction.