P-N Graphene Electromagnetic Wave Detector for High Sensitivity

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Solution Overview

Problem

Conventional electromagnetic wave detectors using graphene as a detection layer face low absorptivity and reduced detection sensitivity due to graphene's ambipolar properties, making it difficult to achieve high sensitivity and OFF operation.

Innovation Solution

The use of p-type and n-type graphene layers, either doped or undoped, in a laminated structure with periodic recesses or protrusions, along with a specific electrode configuration, enhances absorptivity and sensitivity by allowing for differential photocurrent detection and zero dark current operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If graphene is used as an electromagnetic wave detection layer, then the detectable wavelength band is expanded, but detection sensitivity is lowered due to low absorptivity

Engineering Contradiction:

Improvedetectable wavelength bandVSAvoiddetection sensitivity

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent combines p-type graphene and n-type graphene to form a composite detection layer. This composite structure leverages the complementary properties of the two graphene types to achieve both wide wavelength detection and high sensitivity through enhanced absorptivity and differential photocurrent generation.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces periodic recesses or protrusions at specific locations within the graphene detection layer. These localized structural modifications create regions with enhanced electromagnetic wave absorption and photocurrent generation, thereby improving overall detection sensitivity without compromising the wide wavelength band capability.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If graphene is used as an electromagnetic wave detection layer, then the detectable wavelength band is expanded, but OFF operation becomes difficult due to ambipolar property

Engineering Contradiction:

Improvedetectable wavelength bandVSAvoidOFF operation

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

By combining p-type and n-type graphene in a composite structure, the patent exploits the opposite charge carrier behaviors (holes in p-type, electrons in n-type) to achieve ambipolar photodetection. This enables the detector to respond to electromagnetic waves across a wide wavelength band while maintaining the ability to perform OFF operation through differential photocurrent measurement.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent uses a differential detection scheme where p-type and n-type graphene layers act as complementary copies. By measuring the difference between their photocurrents, the system can distinguish between light-induced signals and dark current, enabling effective OFF operation despite the ambipolar nature of graphene.

Inventive Principle:

Principle #26Copying

3Ease of operation

If conventional semiconductor material is used as detection layer, then OFF operation is achieved, but detectable wavelength band is limited by predetermined band gap

Engineering Contradiction:

ImproveOFF operationVSAvoiddetectable wavelength band

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental parameter of the detection layer from conventional semiconductor materials with fixed band gaps to graphene with zero or extremely small band gap. This parameter change enables detection across a wide wavelength band from visible to infrared regions while maintaining OFF operation capability through the differential photocurrent method in p-n type graphene composite.

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 configuration results in a high-sensitivity electromagnetic wave detector with a wide detectable wavelength band, enabling effective OFF operation and polarization-dependent detection without the need for additional polarizers, thus improving system miniaturization and sensitivity.

Implementation Method 1

an electromagnetic wave detector for converting an electromagnetic wave into an electric signal and detecting the electric signal

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentEP3595014B1Electromagnetic wave detector, electromagnetic wave detector array, and electromagnetic wave detection method

Publication Date: 2023.05.17 MITSUBISHI ELECTRIC CORP

Figure 1A~1B
Figure 1C~1D
Figure 2A

AI summary

An electromagnetic wave detector (100) comprises: p-type and n-type graphenes (1, 2) arranged side by side on an insulating layer (5); a first electrode (3) and a second electrode (4) opposing each other via the graphenes (1, 2); a gate electrode for applying an operation voltage to the p-type and n-type graphenes (1, 2); a balance circuit (8) connected between two second electrodes; and a detection circuit (7). The p-type graphene has a Dirac point voltage higher than the operation voltage. The n-type graphene has a Dirac point voltage lower than the operation voltage. In a state in which no electromagnetic wave is incident on the graphenes (1, 2), the balance circuit (8) places the first electrode (3) and the second electrode (4) at the same potential. In a state in which an electromagnetic wave is incident on the p-type and n-type graphenes (1, 2), the detection circuit (7) detects an electric signal between the second electrodes, and outputs an electric signal in the state in which the electromagnetic wave is incident.