Spin Transistor Multiferroic Gate Dielectric Room Temperature Operation
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Solution Overview
Problem
Conventional spin transistors face challenges in achieving carrier-induced ferromagnetism at room temperature, making it difficult to develop effective carrier-mediated paramagnetic-ferromagnetic spin transistors for room temperature applications.
Innovation Solution
A carrier-mediated magnetic phase change spin transistor is developed, utilizing a Dilute Magnetic Semiconductor (DMS) channel with a multiferroic gate dielectric, such as BiFeO3, which enables electrically modulated magnetic exchange bias, enhancing paramagnetic to ferromagnetic switching, and incorporating nanoscale DMS channels like nanowires or quantum wells to promote room temperature operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional spin transistors are used, then device structure is simple, but carrier-induced ferromagnetism cannot be achieved at room temperature
Solution Approach 1:
The patent employs a composite structure combining Dilute Magnetic Semiconductor (DMS) channel with multiferroic gate dielectric (BiFeO3). This composite material system enables carrier-induced ferromagnetism at room temperature through the interaction between carriers in the DMS channel and the multiferroic gate, while maintaining stable ferromagnetic state through the exchange bias mechanism provided by the multiferroic material.
Solution Approach 2:
The patent utilizes parameter changes in the carrier density of the DMS channel to induce ferromagnetic state. By controlling the gate voltage to modulate carrier accumulation in the DMS channel, the material transitions from paramagnetic to ferromagnetic state at room temperature, with the magnetic exchange bias providing stable hysteresis for reliable state maintenance.
2Reliability
If multiferroic gate dielectric is used, then paramagnetic to ferromagnetic switching is enhanced, but device complexity increases
Solution Approach 1:
The multiferroic gate dielectric (BiFeO3) serves multiple functions simultaneously: it acts as the gate insulator, provides magnetic exchange bias to enhance ferromagnetic state stability, and enables electric field control of the DMS channel magnetism. This multi-functionality enhances switching efficiency while the integrated nature of the multiferroic material helps manage the overall device complexity.
3Ease of operation
If carrier-mediated effect is used, then magnetic states can be controlled by electric field, but difficulty in achieving room temperature operation persists
Solution Approach 1:
The patent achieves room temperature operation by changing the parameter of carrier density in the DMS channel through gate-controlled accumulation. The high carrier concentration induced by the gate electric field, combined with the exchange bias from the multiferroic gate dielectric, enables ferromagnetic state stabilization at room temperature while maintaining electric field control capability.
Solution Approach 2:
The composite system of DMS channel and multiferroic gate dielectric creates synergistic effects where the electric field control of the DMS is enhanced by the magnetic properties of the multiferroic material, enabling both ease of operation through electric field control and room temperature functionality through the combined material properties.
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 solution enables efficient paramagnetic to ferromagnetic transitions, increasing on-state current and reducing off-state leakage, thereby improving the on-off ratio and enabling non-voltage characteristics for robust non-volatile memory applications.
Implementation Method 1
The multiferroic material layer enables an electrically modulated magnetic exchange bias that enhances paramagnetic to ferromagnetic switching of the DMS channel
Implementation Method 2
Electric field control of ferromagnetism of DMS has the potential to realize spin Field Effect Transistors (s-FETs) and nonvolatile spin logic devices via carrier mediation
Implementation Method 3
the carriers interact with magnetic ions in the DMS material in such a manner that the DMS material transitions from its normal paramagnetic state to the ferromagnetic state when a large number of carriers are accumulated in the DMS material
Data Source
AI summary
A carrier-mediated magnetic phase change spin transistor is disclosed. In general, the spin transistor includes a Dilute Magnetic Semiconductor (DMS) channel and a gate stack formed on the DMS channel. The gate stack includes a multiferroic gate dielectric on the DMS channel, and a gate contact on a surface of the multiferroic gate dielectric opposite the DMS channel. The multiferroic gate dielectric is formed of a multiferroic material that exhibits a cross-coupling between magnetic and electric orders (i.e., magnetoelectric coupling), which in one embodiment is BiFeO3 (BFO). As a result, the multiferroic material layer enables an electrically modulated magnetic exchange bias that enhances paramagnetic to ferromagnetic switching of the DMS channel. The DMS channel is formed of a DMS material, which in one embodiment is Manganese Germanium (MnGe). In one embodiment, the DMS channel is a nanoscale DMS channel.