Tunnel Field-Effect Transistor Gate Alignment for Low Power
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Solution Overview
Problem
Conventional MOSFET devices face challenges with increasing subthreshold leakage current and power consumption as they approach nanometer sizes, limited by the thermoelectric potential KT/q theory, which prevents a subthreshold slope less than 60 mV/dec and high power consumption in tunnel field-effect transistors.
Innovation Solution
A tunnel field-effect transistor design with source regions on both sides of an oxide structure, an epitaxial layer on the surface of the source region, and a gate structure on the epitaxial layer, aligned to facilitate electron tunneling, enhancing the subthreshold swing and reducing power consumption by optimizing the tunneling area and electric field direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional MOSFET device size is continuously decreased to nanometer scale, then device integration density is improved, but subthreshold leakage current increases and power consumption increases due to inability to achieve subthreshold slope less than 60 mV/dec
Solution Approach 1:
The device is segmented into distinct functional regions including source region, channel region, and drain region with specific doping profiles. The channel region is further segmented into inversion layer and accumulation layer to enable controlled carrier transport and reduce leakage current while maintaining high integration density
Solution Approach 2:
Different regions of the device are assigned different doping concentrations and material compositions optimized for their specific functions. The source region has high doping concentration for carrier injection, the channel region has graded doping for optimal electric field distribution, and the drain region has specific doping for efficient carrier collection, thereby reducing subthreshold leakage while maintaining compact size
2Speed
If threshold voltage is decreased to improve device switching performance, then device speed is improved, but subthreshold leakage current continuously increases due to thermoelectric potential limitation
Solution Approach 1:
The device utilizes dynamic control of the electric field through the gate voltage to modulate the barrier height at the source-channel interface. By applying appropriate gate voltages, the barrier can be dynamically lowered to enable fast switching while maintaining high barrier in off-state to prevent leakage, thus achieving both high speed and low power consumption
Solution Approach 2:
The device employs changes in material parameters such as bandgap energy, effective mass, and doping concentration to optimize the tunneling characteristics. By carefully selecting these parameters, the device achieves steep subthreshold slope with low leakage current while maintaining fast switching speed through optimized carrier injection and transport
3Loss of energy
If tunnel field-effect transistor uses band-to-band tunneling conduction mechanism to achieve super-steep subthreshold slope, then theoretical power consumption is reduced, but actual subthreshold swing value cannot be less than 60 mV/dec and power consumption remains relatively high
Solution Approach 1:
The device structure is designed with preliminary optimization of the band alignment between source and channel regions to facilitate efficient band-to-band tunneling. The doping profiles and interface structures are pre-configured to maximize the tunneling probability and achieve subthreshold swing less than 60 mV/dec, thereby realizing low power consumption in practice
Solution Approach 2:
The device employs composite material structures including different semiconductor materials with complementary bandgaps and effective mass ratios. This composite structure optimizes the tunneling characteristics by creating favorable band alignment and enhancing the tunneling matrix element, thereby achieving both steep subthreshold slope and low actual power consumption
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 design achieves a subthreshold swing value less than 60 mV/dec and low power consumption by improving the tunneling efficiency and reducing leakage currents, addressing the limitations of conventional MOSFET devices at nanometer scales.
Implementation Method 1
a tunnel field-effect transistor (TFET) uses a band-to-band tunneling conduction mechanism
Implementation Method 2
bands of a source region and a channel bend under an action of a gate voltage
Implementation Method 3
an oxide structure, where the oxide structure is located on a surface of the substrate; insulation layers, where the insulation layers are located on the surface of the substrate and two sides of the oxide structure
Implementation Method 4
epitaxial layer, where the epitaxial layer is located on the surface of the insulation layer and a surface on a side that is of the source region and that is away from the oxide structure
Data Source
AI summary
A tunnel field-effect transistor and a method for manufacturing a tunnel field-effect transistor is disclosed. Source regions are located on two sides of an oxide structure, an epitaxial layer is located on a surface on a side that is of the source region and that is away from the oxide structure, and a gate structure is located on a surface on a side that is of the epitaxial layer and that is away from the source region, so that a gate electric field direction of the tunnel field-effect transistor is the same as an electron tunneling direction, and carriers on a valence band of the source region tunnel to a conduction band of the epitaxial layer at relatively high tunneling efficiency, thereby generating a steep subthreshold swing and enabling a subthreshold swing value of the tunnel field-effect transistor to be lower than 60 mV/dec to consume relatively low power.