Ferroelectric p-n Homojunction Capacitor for Stable Negative Capacitance

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Solution Overview

Problem

Existing capacitive devices using ferroelectric-dielectric heterostructures face instability in negative capacitance effects at room temperature and lower frequencies, resulting in limited capacitance enhancement compared to dielectric layers.

Innovation Solution

The design of capacitive devices featuring bi-layer ferroelectric p-n homojunctions with equal doping concentrations, where n-type and p-type ferroelectric layers form a homojunction without non-ferroelectric dielectric materials, stabilizing the negative capacitance effect and increasing equivalent capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferroelectric-dielectric heterostructures are used to achieve negative capacitance effect, then capacitance enhancement is obtained, but instability occurs at room temperature and lower frequencies

Engineering Contradiction:

Improvestability of negative capacitance effectVSAvoidoperating temperature range

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the fundamental parameter of the structure from heterointerface (ferroelectric-dielectric) to homointerface (ferroelectric-ferroelectric with different doping). This parameter change enables the negative capacitance effect to stabilize at room temperature and lower frequencies, resolving the temperature and frequency stability issue while maintaining capacitance enhancement

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite ferroelectric materials with different doping types (n-type and p-type) to form the homojunction. This composite approach combines the benefits of both doped layers to achieve stable negative capacitance at room temperature, overcoming the limitations of conventional ferroelectric-dielectric heterostructures

Inventive Principle:

Principle #40Composite materials

2Reliability

If ferroelectric-dielectric heterostructures are used, then negative capacitance effect is achieved, but capacitance enhancement is limited compared to dielectric layers

Engineering Contradiction:

Improvecapacitance enhancement ratioVSAvoidcapacitance magnitude

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

By changing from heterointerface to homointerface configuration, the patent achieves superior capacitance enhancement (exceeding 100% compared to dielectric layers) while maintaining system stability. The homojunction structure enables both high enhancement ratio and large capacitance magnitude simultaneously

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If conventional ferroelectric-dielectric heterostructures are used, then negative capacitance is achieved, but the effect is transitory and unstable

Engineering Contradiction:

Improvestability of negative capacitanceVSAvoidduration of negative capacitance effect

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of stationary object

Solution Approach 1:

The patent transforms the negative capacitance effect from transitory to steady-state by changing the interface configuration from heterointerface to homointerface. This parameter change extends the duration and stability of the effect, enabling continuous operation at room temperature and lower frequencies

Inventive Principle:

Principle #35Parameter changes

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 achieves a stable, steady-state negative capacitance effect at room temperature and lower frequencies, significantly enhancing capacitance by up to 100% compared to component layers, while maintaining stability across varying voltages and frequencies.

Implementation Method 1

A recently implemented method to increase the capacitance of capacitive devices is the use of the negative capacitance (NC) effect shown by ferroelectric materials

Methodology Applied

Scientific EffectNegative capacitance effect:

Implementation Method 2

Ferroelectric (FE) materials are dielectrics having the ability to spontaneously polarize, whitout the presence of an electric field

Methodology Applied

Scientific EffectSpontaneous polarization:

Data Source

PatentEP4369367A1Capacitive device comprising a ferroelectric p-n homojunction with negative capacitance, method of making the same and use

Publication Date: 2024.05.15 INST NA&TCEDIL IONAL DE CERC DEZVOLTARE PENTRU FIZICA MATERIALELOR

Figure 1.a~2a
Figure 2b

AI summary

The present invention refers to a capacitive device comprising two electrodes (2, 4) separated by a dielectric medium (5), wherein said dielectric medium (5) consists of one or more pairs of ferroelectric (FE) layers (30,32), each pair having a first, n-type FE layer (30) made of an n-doped FE material and a second, p-type FE layer made of a p-doped FE material, wherein said first and second FE layers (30 and 32) form a FE p-n homojunction and have substantially equal doping concentrations. Furthermore, the present invention refers to a method for manufacturing such a capacitive device. Also, the invention refers to the use of a ferroelectric bi-layer forming a p-n homojunction wherein the two layers have substantially equal p-type and n-type doping concentrations in a capacitive device.