Memristive Device Gate Terminal Threshold Voltage Reduction
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Solution Overview
Problem
Conventional memristive memory devices have non-trivial threshold voltages, leading to increased power dissipation and area complexity due to the use of phase change materials.
Innovation Solution
The use of a separate gate terminal offset from the memristive material by an insulator, such as an oxide or ferroelectric material, applies an external electric field to build up charge in the memristive material, thereby reducing the threshold voltage through field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase change materials are used as the active region in memristive devices, then information can be encoded based on phase configuration and resistance, but the threshold voltage becomes non-trivial and power dissipation increases
Solution Approach 1:
An access transistor is introduced as an intermediary component between the control circuit and the memristive device. This transistor acts as a mediator that enables voltage modulation of the memristive material, allowing the threshold voltage to be adjusted without directly increasing the power dissipation of the memristive material itself during information encoding operations.
Solution Approach 2:
The threshold voltage of the memristive device is dynamically changed by modifying the voltage applied to the memristive material through the access transistor. By controlling the voltage parameter through the transistor gate, the threshold voltage can be reduced to lower power dissipation during read and write operations, while maintaining the reliability of information encoding.
2Reliability
If multiple access transistors are attached in series to access memristive memory devices, then voltage distribution ensures no transistor is over-driven, but the areal complexity increases
Solution Approach 1:
The access function is segmented into two distinct components: a first access transistor for voltage modulation and a second access transistor for current control. This segmentation allows each transistor to have a specialized function, reducing the need for multiple series transistors and thereby reducing areal complexity while maintaining voltage protection through functional division.
Solution Approach 2:
The first access transistor is designed to perform multiple functions: it modulates the voltage applied to the memristive material, protects subsequent transistors from over-driving, and enables efficient read and write operations. This multi-functionality reduces the need for separate dedicated transistors for each function, thereby reducing overall device complexity.
3Use of energy by moving object
If the threshold voltage of memristive devices is reduced, then power dissipation decreases, but the device requires additional control mechanisms
Solution Approach 1:
The access transistor serves as an intermediary that provides voltage modulation capability without requiring complex control circuits. By using the transistor's gate voltage control, the threshold voltage of the memristive device can be dynamically adjusted to reduce power dissipation, while the transistor itself acts as a simple and well-understood control element.
Solution Approach 2:
The patent replaces complex voltage control mechanisms with the well-established field effect transistor control mechanism. Instead of requiring complex circuits to modulate voltage and reduce threshold voltage, the invention uses the standard transistor gate voltage control approach, which is a mature and reliable method that simplifies the control mechanism while achieving the desired power reduction.
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
This approach effectively lowers the threshold voltage of memristive devices, reducing power dissipation and area complexity, while also leveraging the non-volatility of ferroelectric materials.
Implementation Method 1
applying a gate voltage to the gate terminal to build up charge in the memristive material, thereby lowering a threshold voltage of the memristive material via field effects
Data Source
AI summary
Techniques for reducing a threshold voltage of memristive devices via field effects are provided. In one aspect, a memristive device includes: a memristive material; multiple electrodes directly contacting the memristive material; and a gate terminal separated from the memristive material by an electrical insulator. The memristive device can be implemented as one of multiple memristive devices in a unit cell with a gate word line connected to the gate terminal of each of the multiple memristive devices in the unit cell. A method for operating the present memristive devices is also provided.