Graphene Photodetector with Separated Drain Electrode
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Solution Overview
Problem
Existing graphene-semiconductor heterojunction photodetectors face limitations in controlling the Fermi level and Schottky barrier height, leading to low photoresponsivity and difficulty in adjusting gain according to varying environmental conditions.
Innovation Solution
A graphene-semiconductor heterojunction photodetector design with a gate electrode having light transmittance, a physically separated drain electrode, and an intermediate layer between the substrate and graphene layer, allowing for control of dark current and photoresponsivity through gate voltage adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Schottky junction is formed between graphene layer and silicon substrate with gate electrode on rear surface, then photocurrent is generated throughout entire interface improving photoresponsivity, but Fermi level of graphene layer cannot be controlled and Schottky barrier height cannot be precisely controlled
Solution Approach 1:
The device is divided into distinct functional regions: a light-receiving region where the graphene-silicon heterojunction is formed for photocurrent generation, and a gate control region where the gate electrode is positioned to control the Fermi level and Schottky barrier height independently. This segmentation allows simultaneous achievement of high photoresponsivity through interface photocurrent and precise control through gate voltage adjustment.
Solution Approach 2:
An intermediate layer is introduced between the graphene layer and the silicon substrate. This intermediate layer serves as a mediator that enables precise control of the Schottky barrier height while maintaining the photocurrent generation capability at the graphene-silicon interface. The intermediate layer acts as a tuning element that decouples the barrier control from the photocurrent generation process.
2Adaptability or versatility
If gain is adjusted according to electric field from gate in existing photodetectors, then photosensitivity can be adapted to various environments, but existing gate structures cannot achieve precise control due to opaque metal gates and rear surface positioning
Solution Approach 1:
The gate electrode is designed with light transmittance and positioned in the light-receiving region, enabling control of the electric field parameter throughout the active area. By adjusting the gate voltage, the Fermi level and Schottky barrier height are precisely controlled, which in turn adjusts the gain and photosensitivity parameters to adapt to various environmental conditions with high precision.
3Device complexity
If drain electrode is in physical contact with graphene layer for current collection, then simple structure is achieved, but dark current increases and photodetection efficiency decreases
Solution Approach 1:
The drain electrode is extracted from direct contact with the graphene layer in the light-receiving region. Instead, the drain electrode is positioned adjacent to the graphene layer with a controlled separation. This extraction eliminates the dark current path through direct contact while maintaining efficient photocurrent collection through the prescribed geometric arrangement, thereby improving photodetection efficiency.
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 design enhances photosensitivity, output voltage, and photodetection efficiency by reducing dark current and enabling adjustable photoresponsivity according to environmental conditions.
Implementation Method 1
a gate electrode formed on the gate insulating layer and having light transmittance
Implementation Method 2
a photodetector has a structure in which, when light is incident on an active region, the light induces a change in current to form a photocurrent
Implementation Method 3
a Schottky junction is formed between the graphene layer 20 and the silicon substrate 10, thereby forming a diode structure. When light is incident, a photocurrent is generated, and the photocurrent occurs throughout the entire interface between the graphene layer 20 and the silicon substrate 10
Implementation Method 4
there is a limitation in controlling the Fermi level of the graphene layer 20 because the silicon substrate 10 itself acts as a portion of the gate electrode 60 or the gate electrode 60 acts on the rear surface thereof
Data Source
AI summary
In a graphene-semiconductor heterojunction photodetector and a method of manufacturing the same according to the present inventive concept, a source electrode and a test electrode are formed to face each other on a graphene layer, and a drain electrode is formed in a direction perpendicular to a central region portion of the graphene layer, so that the drain electrode may be physically separated from the graphene layer. Further, charges formed at the central region portion of the graphene layer are transmitted to the drain electrode through a substrate, so that high photosensitivity may be secured, and a high output voltage may be secured for the applied light. Accordingly, the drain electrode is formed at a side surface of the graphene layer, so that the size of the drain electrode may be easily controlled, and a high output voltage may be obtained.