2D-EFET Transistor Using Electrostrictive Gate for Sub-60 mV/Decade Switching
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Solution Overview
Problem
Conventional MOSFETs face challenges in scaling beyond 10 nm due to material limitations, leading to increased power and heat dissipation, and require steep subthreshold swing and high ON-state current densities for efficient performance, which existing devices like tunneling FETs and piezoelectric strain modulated Si FinFETs struggle to achieve.
Innovation Solution
A two-dimensional electrostrictive field effect transistor (2D-EFET) utilizing an electrostrictive or piezoelectric or ferroelectric material gate that applies mechanical stress to a 2D channel, dynamically reducing its bandgap from insulator to metal, enabling sub-60 mV/decade subthreshold swing and high ON-state current through voltage-induced strain transduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional MOSFET scaling is continued beyond 10 nm, then device density increases, but power and heat dissipation increase exponentially
Solution Approach 1:
The patent changes the fundamental operating parameter of the transistor by using electrostrictive or piezoelectric materials in the gate that can dynamically alter the bandgap of the 2D channel material through strain-induced lattice constant changes. This allows the device to operate beyond Boltzmann statistics with sub-60 mV/decade subthreshold swing, enabling continued scaling without exponential power increase
Solution Approach 2:
The patent employs composite material structures combining 2D channel materials (such as MoS2, WSe2) with electrostrictive/piezoelectric gate materials. This composite approach enables both high device density through 2D material integration and low power consumption through the unique electromechanical coupling properties of the piezoelectric gate that provides steep subthreshold characteristics
2Loss of energy
If voltage scaling is implemented to reduce power consumption, then OFF state current decreases, but subthreshold swing cannot go below 60 mV/decade due to Boltzmann statistics
Solution Approach 1:
The patent replaces the conventional electrical field control mechanism with an electromechanical coupling mechanism. The electrostrictive/piezoelectric gate material converts electrical input into mechanical strain that directly modulates the channel bandgap, bypassing the Boltzmann statistical limitation that governs conventional electrical field-effect control
Solution Approach 2:
The patent utilizes the phase transition capability of 2D materials where the bandgap can be dynamically tuned from insulating to metallic states through strain-induced lattice constant changes. This phase transition mechanism enables abrupt switching characteristics with sub-60 mV/decade subthreshold swing, allowing simultaneous achievement of low OFF state current and steep switching
3Speed
If dimension scaling is pursued to increase integration density, then transistor speed increases, but power density increases at the same rate
Solution Approach 1:
The patent changes the voltage scaling parameter by enabling operation at lower supply voltages through sub-60 mV/decade subthreshold swing. The electrostrictive/piezoelectric gate mechanism allows the device to maintain high ON state current and fast switching speed even at reduced voltage levels, thereby increasing integration density without proportionally increasing power density
4Loss of energy
If tunneling FETs are used to achieve sub-60 mV/decade subthreshold swing, then power consumption decreases, but ON state current density is limited by large tunneling barriers
Solution Approach 1:
The patent changes the switching mechanism parameter from quantum tunneling (which limits current density) to strain-induced bandgap modulation. The electrostrictive/piezoelectric gate provides mechanical strain that continuously tunes the channel bandgap, enabling both low power consumption through sub-60 mV/decade subthreshold swing and high ON state current density by eliminating large tunneling barriers
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 2D-EFET achieves aggressive channel length scaling, low power consumption, and high performance by maintaining a sub-60 mV/decade subthreshold swing and significantly higher ON-state current density compared to traditional FETs, addressing the limitations of existing devices.
Implementation Method 1
The gate has a column of an electrostrictive or piezoelectric or ferroelectric material, wherein an electrical input to the gate produces an elongation of the column that applies a force or stress on the channel
Implementation Method 2
The gate has a column of an electrostrictive or piezoelectric or ferroelectric material, wherein an electrical input to the gate produces an elongation of the column that applies a force or stress on the channel
Implementation Method 3
an electrical input to the gate produces an elongation of the column that applies a force or stress on the channel and reduces the bandgap of the two-dimensional material. The change in the bandgap of the two dimensional material changes its conductivity
Data Source
AI summary
A device and method for manufacturing a two-dimensional electrostrictive field effect transistor having a substrate, a source, a drain, and a channel disposed between the source and the drain. The channel is a two-dimensional layered material and a gate proximate the channel. The gate has a column of an electrostrictive or piezoelectric or ferroelectric material, wherein an electrical input to the gate produces an elongation of the column that applies a force or mechanical stress on the channel and reduces a bandgap of two-dimensional material such that the two-dimensional electrostrictive field effect transistor operates with a subthreshold slope that is less than 60 mV/decade.