Graded InP Buffer for Silicon Transistors
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Solution Overview
Problem
Current methods for forming transistor structures using Group III-V semiconductor materials face challenges in achieving high crystal quality, particularly due to lattice mismatch issues between silicon substrates and indium phosphide channels, leading to defects and reduced carrier mobility.
Innovation Solution
A multilayer buffer structure with graded indium concentration is used on a silicon substrate to accommodate lattice mismatch, enabling epitaxial growth of high-quality indium phosphide and other Group III-V materials with minimal defects, facilitating the formation of defect-free nanowire or nanoribbon transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon substrate is used directly for growing indium phosphide channel, then the manufacturing process is simple, but the crystal quality deteriorates due to lattice mismatch causing defects
Solution Approach 1:
A buffer structure comprising multiple layers (GaP layer on silicon substrate, followed by InGaP layers with graded indium concentration) is introduced as an intermediary between the silicon substrate and the indium phosphide channel. This buffer structure gradually transitions the lattice constant to match that of indium phosphide, reducing lattice mismatch and enabling high-quality crystal growth without directly growing indium phosphide on silicon.
Solution Approach 2:
The indium concentration in the buffer layers is gradually changed from 0% in the GaP layer to 100% in the top InP layer, with intermediate InGaP layers having graded indium concentrations (e.g., 25%, 50%, 75%). This parameter change in composition allows progressive lattice constant adjustment, minimizing defects while maintaining manufacturing feasibility.
2Reliability
If high-quality indium phosphide channel is achieved through buffer structure, then carrier mobility is improved, but device complexity increases
Solution Approach 1:
The buffer structure uses a systematic parameter change approach with graded indium concentration layers (GaP → In0.25Ga0.75P → In0.50Ga0.50P → In0.75Ga0.25P → InP), where each layer has a specific indium concentration that progressively matches the target InP lattice constant. This controlled parameter transition achieves high crystal quality while keeping the buffer structure manageable in complexity.
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 approach results in transistors with improved crystal quality, enhanced carrier mobility, and increased operating voltage, enabling further scaling and performance enhancement of semiconductor devices.
Implementation Method 1
enabling epitaxial growth of high-quality indium phosphide and other Group III-V materials with minimal defects
Data Source
AI summary
An integrated circuit with at least one transistor is formed using a buffer structure on the substrate. The buffer structure includes one or more layers of buffer material and comprises indium, gallium, and phosphorous. A ratio of indium to gallium in the buffer structure increases from a lower value to a higher value such that the buffer structure has small changes in lattice constant to control relaxation and defects. A source and a drain are on top of the buffer structure and a body of Group III-V semiconductor material extends between and connects the source and the drain. A gate structure wrapped around the body, the gate structure including a gate electrode and a gate dielectric, wherein the gate dielectric is between the body and the gate electrode.