Reverse-Mesa Ridge Structure for Integrated Optical Devices
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Solution Overview
Problem
The existing method for producing integrated optical devices with a butt-joint structure faces challenges in achieving a large width at the upper end and a small width at the lower end of the ridge structure due to the formation of stepped structures caused by the side-etching layer, which complicates the optimization of the ridge structure dimensions.
Innovation Solution
The method involves growing a first stacked semiconductor layer with a side-etching layer of different composition, selectively etching to form an overhang, and growing a second stacked semiconductor layer under specific conditions, including a lower growth temperature and higher V/III ratio for the cladding layer, to increase the thickness of the first cladding layer and suppress recess formation, thereby achieving a larger upper end width and smaller lower end width of the ridge structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a side-etching layer is used to form the ridge structure, then the ridge structure can be formed with specific crystal planes, but stepped structures are formed due to etching rate differences, making it difficult to achieve a large upper end width and small lower end width
Solution Approach 1:
The patent removes the side-etching layer from the ridge structure formation process. Instead of using a multi-layer structure with side-etching layer, InP upper cladding layer, and InP lower cladding layer, the invention directly forms the ridge structure by etching the InP upper cladding layer and InP lower cladding layer, thereby eliminating the stepped structures caused by differential etching rates and simplifying the overall structure while achieving the desired reverse-mesa geometry
Solution Approach 2:
The patent segments the ridge structure formation into distinct etching steps: first etching the InP upper cladding layer to form the upper portion of the ridge, then etching the InP lower cladding layer to form the lower portion. This segmentation allows independent control of upper and lower ridge dimensions, enabling the upper end width to be made larger than the lower end width to achieve the reverse-mesa structure
2Manufacturing precision
If the thickness of the InP upper cladding layer is increased to achieve large upper end width and small lower end width, then the contact area increases and contact resistance decreases, but recesses are formed on the surface of the InP upper cladding layer
Solution Approach 1:
The patent changes the growth parameters of the InP upper cladding layer, specifically controlling the thickness to be 1.41 μm or more. This parameter change ensures that when the ridge structure is formed by etching, the upper end width can be sufficiently large and the lower end width can be sufficiently small, achieving the reverse-mesa structure without forming recesses on the surface
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 approach effectively increases the width of the upper end of the ridge structure while minimizing the lower end width, enhancing the contact area and reducing contact resistance, and prevents recess formation on the cladding layer surface, resulting in improved optical device performance.
Implementation Method 1
the side-etching layer 117 is selectively etched by wet etching to form an overhang between the mask 118 and the InP upper cladding layer 116
Implementation Method 2
a second stacked semiconductor layer 120 including a second optical waveguiding layer 124 coupled to the first optical waveguiding layer 114 and a second cladding layer 126 positioned on the second optical waveguiding layer 124 are selectively grown on the substrate 102 through the mask 118
Implementation Method 3
a reverse-mesa ridge structure by etching the first and second cladding layers through a second etching mask formed on the first and second stacked semiconductor layers
Data Source
AI summary
A method for producing an integrated optical device includes the steps of growing a first stacked semiconductor layer including a first optical waveguiding layer, a first cladding layer, and a side-etching layer; etching the first stacked semiconductor layer through a first etching mask; growing, a second stacked semiconductor layer including a second optical waveguiding layer and a second cladding layer through the first etching mask; and forming a reverse-mesa ridge structure by etching the first and second cladding layers. The step of etching the first stacked semiconductor layer includes a step of forming an overhang by etching the side-etching layer by wet etching. In the step of growing the second stacked semiconductor layer, the second cladding layer is grown at a lower growth temperature and a higher V/III ratio comparing to those in the growth of the second optical waveguiding layer.