BJT Superlattice Structure for Carrier Mobility and Dopant Blocking
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Solution Overview
Problem
Current semiconductor devices face limitations in achieving enhanced performance due to challenges in carrier mobility and dopant diffusion, which affect the efficiency and reliability of bipolar junction transistors.
Innovation Solution
The development of a bipolar junction transistor (BJT) incorporating a superlattice structure with stacked groups of semiconductor and non-semiconductor monolayers, which reduces the effective mass of charge carriers and acts as a dopant barrier, enhancing mobility and reducing unwanted scattering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional semiconductor structures are used, then manufacturing is simpler, but charge carrier mobility is limited due to scattering effects
Solution Approach 1:
The base and collector regions are segmented into multiple thin semiconductor monolayers separated by non-semiconductor monolayers, forming a superlattice structure. This segmentation reduces the effective mass of charge carriers and minimizes scattering effects, thereby enhancing charge carrier mobility while managing the increased structural complexity through systematic layering
Solution Approach 2:
The patent employs composite material structures where semiconductor monolayers (e.g., Si, Ge, SiGe) are combined with non-semiconductor monolayers (e.g., SiO2, SiC, diamond) to create superlattices. This composite approach optimizes charge carrier mobility by reducing scattering while maintaining structural integrity and enabling selective dopant blocking
2Reliability
If dopant diffusion is allowed for device fabrication, then manufacturing is easier, but device reliability deteriorates due to unwanted dopant distribution
Solution Approach 1:
Non-semiconductor monolayers (e.g., SiO2, SiC, diamond) are introduced as intermediary barrier layers between doped semiconductor regions. These intermediary layers effectively block dopant diffusion during fabrication processes, ensuring precise dopant distribution and enhancing device reliability without significantly complicating the manufacturing workflow
Solution Approach 2:
The superlattice structure implements local quality by placing dopant-blocking non-semiconductor monolayers at specific interfaces where dopant diffusion must be prevented, while maintaining dopant permeability in other regions. This localized approach ensures reliable dopant distribution control only where needed, balancing manufacturing ease with device reliability
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 superlattice structure in BJTs results in improved charge carrier mobility and effective dopant blocking, leading to enhanced performance and reliability by reducing dopant diffusion and scattering, while maintaining compatibility with existing semiconductor processing techniques.
Implementation Method 1
The first superlattice may include a first plurality of stacked groups of first layers, with each group of first layers including a first plurality of stacked base semiconductor monolayers defining a first base semiconductor portion, and at least one first non-semiconductor monolayer constrained within a crystal lattice of adjacent first base semiconductor portions
Implementation Method 2
The superlattice structure in BJTs results in improved charge carrier mobility and effective dopant blocking, leading to enhanced performance and reliability by reducing dopant diffusion and scattering
Data Source
AI summary
A method for making a bipolar junction transistor (BJT) may include forming a first superlattice on a substrate defining a collector region therein. The first superlattice may include a plurality of stacked groups of layers, with each group of layers comprising a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions. The method may further include forming a base on the first superlattice, and forming a second superlattice on the base comprising a plurality of stacked groups of layers, with each group of layers comprising a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions. The method may also include forming an emitter on the second superlattice.