Tunneling Field Effect Transistor Heterojunction Band Alignment
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Solution Overview
Problem
Tunneling field effect transistors (TFETs) face challenges in achieving high ON current and steep ON/OFF operation due to the quantum tunneling phenomenon, which limits their practical application.
Innovation Solution
A TFET design featuring a heterojunction between a p-type group IV semiconductor and an n-type oxide semiconductor, with a type-II energy band structure, where the energy band alignment allows for increased ON current and controlled tunneling, utilizing materials like Si, Ge, and ZnO to optimize the band structure and tunneling probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a tunneling field effect transistor uses the quantum tunneling phenomenon for operation, then steep ON/OFF operation is enabled, but the current value in ON state is insufficient
Solution Approach 1:
The patent employs a heterojunction structure combining two different semiconductor materials with distinct band structures (e.g., wide-bandgap material and narrow-bandgap material) to create a type-II band alignment. This composite material approach enables both steep subthreshold swing through quantum tunneling and enhanced ON current through optimized band offset, resolving the contradiction between switching speed and ON state current magnitude.
Solution Approach 2:
The patent optimizes critical parameters including band offset energy difference, depletion layer width, and tunneling barrier thickness to simultaneously achieve steep subthreshold swing and high ON current. By carefully controlling the energy band alignment and physical dimensions of the heterojunction, the device maintains quantum tunneling benefits while improving carrier injection efficiency.
2Quantity of substance
If the current value in ON state is increased for practical use, then the transistor becomes more useful, but the steep ON/OFF operation characteristic is lost
Solution Approach 1:
The heterojunction structure with type-II band alignment allows the patent to decouple the mechanisms controlling ON current and subthreshold swing. The wide-bandgap material provides high breakdown voltage and low leakage (steep OFF), while the narrow-bandgap material provides high carrier concentration and mobility (high ON current), achieving both goals simultaneously.
Solution Approach 2:
The patent creates different functional regions within the semiconductor structure: a tunneling region with specific band alignment for steep switching, and a channel region optimized for high current flow. This local differentiation of material properties and structural characteristics allows simultaneous optimization of both switching speed and ON current.
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 high ON current and steep ON/OFF switching with a sub-threshold swing of 71 mV/dec, and an ON/OFF current ratio exceeding 10^8, demonstrating improved performance in low-power operation.
Implementation Method 1
a tunneling field effect transistor (which may be hereinafter referred to as "TFET") using the quantum tunneling phenomenon as a new operation principle has attracted attention. By using the quantum tunneling phenomenon, operation not following temperature and electron statistical distributions, that is, steep ON/OFF operation with a small sweep voltage width, is enabled.
Implementation Method 2
The first semiconductor layer and the second semiconductor layer may be a material having an energy band structure forming a type-II band structure by the heterojunction. The second semiconductor layer may be a material in which energy of a conduction band minimum is present in a band gap of the first semiconductor layer.
Data Source
AI summary
A tunneling field effect transistor according to an embodiment of the present invention includes: a first semiconductor layer having a first conductive type; a second semiconductor layer having a second conductive type and realizing a heterojunction with respect to the first semiconductor layer in a first region; a gate insulating layer over the second semiconductor layer in the first region; a gate electrode layer over the gate insulating layer; a first electrode layer electrically connected to the first semiconductor layer; a second electrode layer electrically connected to the second semiconductor layer; and a first insulating layer interposed between the first semiconductor layer and the second semiconductor layer in a second region adjacent to the first region toward the second electrode layer.