Optical Semiconductor Spot Size Converter with Inclined Terraces

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Solution Overview

Problem

Optical semiconductor integrated devices face challenges in design flexibility and light coupling loss due to the difference in spot sizes between the device's end face and optical fiber, particularly when forming burying layers with chlorine-containing gases, which limits the orientation of mesa structures and affects the thickness of cladding layers.

Innovation Solution

The implementation of a waveguide unit with a spot size converting unit and terraces on a semiconductor substrate, where the terraces' orientation tilts relative to the waveguide, allowing for a burying layer to be formed with a higher upper end position, thereby enhancing light coupling by adjusting the interval and orientation of these structures to match the optical fiber's spot size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a burying layer is formed using chlorine-containing gas to suppress lateral growth, then the burying layer thickness becomes uniform, but the upper end position of the burying layer becomes lower, reducing light coupling efficiency

Engineering Contradiction:

Improveburying layer thickness uniformityVSAvoidlight coupling loss

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The patent introduces a terrace structure with inclined surfaces at specific crystallographic orientations ([0-11] direction) to control the burying layer growth. By utilizing the vertical dimension and inclined surfaces, the burying layer is guided to grow upward along the terrace facets rather than laterally, achieving both thickness uniformity and high upper end position for effective light coupling.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the crystallographic orientation parameter of the terrace surfaces to [0-11] direction and controls the inclination angle to achieve optimal growth direction. By adjusting these geometric parameters, the burying layer growth is directed vertically upward while maintaining uniform thickness, resolving the contradiction between thickness control and coupling efficiency.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the mesa structure orientation is tilted toward the [0-11] direction to enable terrace formation, then design flexibility improves, but the burying layer growth pattern changes, potentially covering the mesa top

Engineering Contradiction:

Improvedesign flexibilityVSAvoidmesa structure configuration

Core Design Contradiction:

Adaptability or versatilityVSShape

Solution Approach 1:

The patent introduces asymmetric terrace structures with inclined surfaces at specific orientations relative to the mesa structure. The terraces are formed with inclined surfaces having [0-11] direction components, creating an asymmetric configuration that guides burying layer growth in a controlled manner while maintaining design flexibility for various device layouts.

Inventive Principle:

Principle #4Asymmetry

3Ease of manufacture

If the mesa unit extends to the cleavage position with [011] orientation, then the burying layer does not cover the mesa top, but design flexibility is limited

Engineering Contradiction:

Improveburying layer formation simplicityVSAvoiddesign flexibility

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent segments the device structure into distinct components: the mesa unit, the terrace structure with inclined surfaces, and the burying layer. This segmentation allows independent optimization of each component - the mesa can be positioned flexibly while the terrace structure controls the burying layer growth, enabling both manufacturing simplicity and design flexibility.

Inventive Principle:

Principle #1Segmentation

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 reduces light coupling loss by matching the spot sizes of the optical semiconductor device with the optical fiber, improving design flexibility and operational efficiency while maintaining the structural integrity of the mesa units.

Implementation Method 1

a stripe-shaped mesa unit is buried by using the metal organic vapor phase epitaxy (MOVPE)

Methodology Applied

Scientific EffectMetal organic vapor phase epitaxy (MOVPE): Chemical Vapour Deposition

Data Source

PatentUS8938138B2Optical semiconductor device and method of manufacturing optical semiconductor device

Publication Date: 2015.01.20 FUJITSU LTD

AI summary

An optical semiconductor device includes: a waveguide unit which is formed on a semiconductor substrate including a (100) plane and includes a core layer which propagates light; a spot size converting unit which is formed on the semiconductor substrate, is optically connected to the waveguide unit, and converts diameter of light propagated; and a pair of terraces which are formed on the semiconductor substrate and are opposed to each other while sandwiching the spot size converting unit. Interval between opposed units which are opposed to each other while sandwiching the spot size converting unit in the pair of terraces changes, and each of the opposed units includes a part whose orientation tilts to a [0-11] direction with respect to a [011] direction, and position of an upper end of the spot size converting unit is higher than that of an upper end of the waveguide unit.