Graphene Optoelectronic Detector Using Negative Photoconductivity

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Solution Overview

Problem

Conventional optoelectronic detectors using graphene are not suitable for positive photoconductive applications due to low light absorption, and existing sensing materials like ITO or GaN are expensive and inefficient.

Innovation Solution

A graphene optoelectronic detector with a high-drift carrier moving region and a low-drift carrier moving region is designed, where photonic and electromagnetic energy causes charge carriers to scatter from the high-drift region to the low-drift region, resulting in negative differential photoconductivity, allowing for effective detection of energy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If graphene is used as sensing material in conventional positive photoconductive optoelectronic detectors, then the detector can achieve high transmittance and low cost, but the detection effect is poor due to light absorption rate less than 3%

Engineering Contradiction:

Improvemanufacturing costVSAvoiddetection effect

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent inverts the conventional positive photoconductive detection approach by utilizing negative photoconductivity in graphene. Instead of relying on light absorption to increase conductivity, the invention detects light-induced decreases in conductivity caused by carrier scattering from high-drift to low-drift regions, achieving effective detection despite low light absorption rate

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the detection parameter from conductivity increase (positive photoconductivity) to conductivity decrease (negative photoconductivity). By measuring the reduction in electrical conductivity when carriers scatter from high-drift to low-drift regions under illumination, the system achieves sensitive detection without requiring high light absorption

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If conventional sensing materials like ITO or GaN are used, then the detector can achieve good sensing effect, but the manufacturing cost is high

Engineering Contradiction:

Improvesensing effectVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive sensing materials (ITO, GaN, AlGaAs) with inexpensive graphene while maintaining detection functionality. The invention demonstrates that graphene, despite being cheaper and thinner, can achieve effective sensing through the negative photoconductivity mechanism, eliminating the need for costly conventional materials

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Length of moving object

If graphene is used to substitute conventional sensing materials, then the detector achieves thin thickness and low cost, but the light absorption rate remains less than 3%

Engineering Contradiction:

ImprovethicknessVSAvoidlight absorption rate

Core Design Contradiction:

Length of moving objectVSUse of energy by moving object

Solution Approach 1:

The patent converts the limitation of low light absorption rate into a benefit by using the scattered carriers in low-drift regions as the detection signal. Instead of needing high absorption to generate more carriers, the system detects the scattering effect itself, where even a small number of absorbed photons cause measurable conductivity changes through carrier redistribution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 detector achieves a higher electrical conductivity without applied energy compared to with applied energy, enabling efficient detection of photonic and electromagnetic energy, such as light and magnetic fields, with improved sensitivity and cost-effectiveness.

Implementation Method 1

the photonic and electromagnetic energy may cause charge carriers to be transferred by carrier-carrier scattering in real space, unlike intervalley scattering in the momentum-space (K-space) in some semiconductors, between two real-space regions, where charge carriers move at different speeds

Methodology Applied

Scientific EffectNegative differential photoconductivity: Photoconductivity

Implementation Method 2

charge carriers in a high-drift carrier moving region can be transferred to another low-drift carrier moving region, resulting in a reduction of the total electrical conductivity for both the high-drift and low-drift carrier moving regions

Methodology Applied

Scientific EffectCarrier-carrier scattering: Scattering

Data Source

PatentUS9620597B2Graphene optoelectronic detector and method for detecting photonic and electromagnetic energy by using the same

Publication Date: 2017.04.11 NAT CHENG KUNG UNIV

AI summary

A graphene optoelectronic detector is disclosed, which comprises: an insulating substrate with a graphene layer disposed thereon; a first electrode disposed on the graphene layer or between the graphene layer and the insulating substrate; and a second electrode disposed on the graphene layer or between the graphene layer and the insulating substrate, wherein there is a predetermined distance between the first electrode and the second electrode, and the first electrode and the second electrode are at different electrical potentials, wherein a high-drift carrier moving region is disposed between the first electrode and the second electrode, and a low-drift carrier moving region is disposed outside the high-drift carrier moving region. In addition, the present invention further provides a method for detecting photons and electromagnetic energy using the aforementioned graphene detector.