Tunnel FET-HEMT Structure for Low Subthreshold and Higher Current
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Solution Overview
Problem
Conventional tunnel-field-effect transistors have a small current value compared to MOSFETs due to tunnel transport, limiting their performance and integration density in semiconductor microprocessors.
Innovation Solution
Combining a tunnel-field-effect-transistor (TFET) structure with a high-electron-mobility-transistor (HEMT) structure to generate tunneling and two-dimensional electron gas using a single gate electrode, enhancing current value and subthreshold coefficient performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional tunnel-field-effect transistor structure is used, then a subthreshold coefficient of 60 mV/decade or smaller can be achieved, but the current value becomes significantly small compared to MOSFETs
Solution Approach 1:
The patent combines the TFET structure and HEMT structure into a single integrated device. The TFET portion provides the tunneling mechanism for sub-60mV/decade subthreshold coefficient, while the HEMT portion provides high electron mobility for increased current value. This merging of two different transistor structures resolves the contradiction between achieving low subthreshold coefficient and maintaining high current value.
Solution Approach 2:
The patent employs composite material structures including group IV semiconductor substrates, group III-V compound semiconductor nanowires, and heterostructure layers. These composite materials enable both the quantum tunneling effect needed for low subthreshold coefficient and the high electron mobility required for high current value, resolving the performance contradiction.
2Productivity
If the size of CMOS transistors is reduced to improve integration density, then more transistors can be mounted on one microchip, but leakage current increases due to short channel effect
Solution Approach 1:
The patent replaces the conventional diffusion-based carrier transport mechanism with a quantum tunneling mechanism. This substitution enables the transistor to achieve sharp turn-on/off characteristics without suffering from short channel effects, allowing continued scaling for higher integration density while maintaining low leakage current.
Solution Approach 2:
The patent changes the fundamental operating parameter from diffusion-based transport to tunneling-based transport. This parameter change allows the device to operate with steep subthreshold slopes and low leakage current even at scaled dimensions, enabling high integration density without the penalty of increased leakage.
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 combined TFET and HEMT structure achieves a subthreshold coefficient of 60 mV/decade or smaller while increasing current value, improving integration density and reducing power consumption in semiconductor microprocessors.
Implementation Method 1
a gate electrode that operates such that an electric field acts on the channel to cause tunneling at a junction of the channel on the source electrode side
Implementation Method 2
generating two-dimensional electron gas in the channel while causing the tunneling
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The tunnel field effect transistor according to the present invention has: a channel; a source electrode connected directly or indirectly to one end of the channel; a drain electrode connected directly or indirectly to the other end of the channel; and a gate electrode for causing an electric field to act on the channel, generating a tunnel phenomenon at the source electrode-side joint part of the channel, and simultaneously generating a two-dimensional electron gas in the channel.