Doped Semiconductor Tunnel Barrier for High-VCMA Magnetic Memory

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Solution Overview

Problem

Current memory-centric computing solutions, such as memristors and current-controlled spin-transfer torque memory, fail to meet the demand for low-power and high-speed memory operation with high integration density, particularly due to low voltage-controlled magnetic anisotropy (VCMA) coefficients in existing magnetic tunnel junctions.

Innovation Solution

Magnetic memory devices with a sandwich structure of ferromagnetic layers separated by a doped semiconductor tunnel barrier layer, such as Ga2O3, which forms a Schottky barrier and enhances VCMA via the Rashba-Edelstein effect, allowing for tunable built-in electric fields and increased VCMA parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If current-controlled spin-transfer torque (STT) is used to control magnetism, then magnetic switching can be achieved, but energy efficiency is poor and integration density is limited

Engineering Contradiction:

Improveenergy efficiencyVSAvoidintegration density

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent replaces current-controlled STT mechanism with voltage-controlled magnetic anisotropy (VCMA) mechanism. Instead of using spin-polarized current to switch magnetism, the invention uses electric field to control magnetic anisotropy energy, thereby reducing energy consumption and enabling better scaling for high-density memory applications

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the control parameter from current to voltage. By applying voltage across the tunnel barrier, the magnetic anisotropy is controlled through electric field-induced interfacial anisotropy changes, achieving lower energy dissipation and improved integration density compared to current-based control

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If VCMA is used to control magnetism, then energy efficiency improves, but VCMA parameter is too low (<100 fJ/Vm) for high-density applications

Engineering Contradiction:

Improveenergy efficiencyVSAvoidVCMA parameter

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs composite material structures including CoFeB/CoFeB, CoFeB/MgO/CoFeB, and CoFeB/Ga2O3/CoFeB magnetic tunnel junctions. These composite structures leverage the beneficial properties of each material to achieve enhanced VCMA parameters exceeding 500 fJ/Vm while maintaining low energy consumption

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention introduces doped semiconductor layers (n-type or p-type Ga2O3) at the tunnel barrier to create localized regions with enhanced Rashba-Edelstein effect. This local modification at the interface significantly boosts the VCMA parameter without affecting the overall device structure

Inventive Principle:

Principle #3Local quality

3Loss of energy

If write voltage is reduced for low power consumption, then energy dissipation decreases, but magnetic switching reliability may be compromised

Engineering Contradiction:

Improveenergy dissipationVSAvoidmagnetic switching reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent optimizes multiple parameters including tunnel barrier thickness (1-3 nm), doping concentration (10^19-10^21 atoms/cm³), and layer compositions to achieve the optimal balance between low write voltage and high switching reliability. The doped semiconductor layer creates built-in electric fields that enhance spin-orbit coupling, enabling reliable switching at reduced voltages

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The doped semiconductor tunnel barrier acts as an intermediary that mediates between the applied voltage and the magnetic layers. It generates enhanced Rashba-Edelstein effect and interfacial Dzyaloshinskii-Moriya interaction, enabling efficient magnetization switching at low voltages with high reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces write voltage and energy dissipation, achieving VCMA parameters greater than 500 fJ/Vm, enabling improved integration density and scalability to smaller device dimensions while maintaining low power consumption.

Implementation Method 1

The devices comprise a first ferromagnetic layer, a second ferromagnetic layer, and a tunnel barrier layer composed of a doped semiconductor (instead of an insulator or a dielectric) between the first and second ferromagnetic layers and forming at least one ferromagnetic-doped semiconductor interface

Methodology Applied

Scientific EffectSchottky barrier:

Implementation Method 2

which forms a Schottky barrier and enhances VCMA via the Rashba-Edelstein effect, allowing for tunable built-in electric fields and increased VCMA parameters

Methodology Applied

Scientific EffectRashba-Edelstein effect:

Data Source

PatentUS11930719B2Magnetic memory device using doped semiconductor layer

Publication Date: 2024.03.12 WETA DIGITAL LTD

AI summary

Magnetic memory devices are provided. The devices comprise a first ferromagnetic layer, a second ferromagnetic layer, and a tunnel barrier layer composed of a doped semiconductor (instead of an insulator or a dielectric) between the first and second ferromagnetic layers and forming at least one ferromagnetic-doped semiconductor interface.