ZJU Professor Shisheng Lin’s team -The Graphene/GaAs Schottky Interface: A New Breakthrough Expanding the Spectrum Range

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Highlights

The research article was published by Shisheng Lin from Zhejiang University et.al.

Graphene/GaAs heterostructure photodetectors fabricated
Ag nanoparticles added for plasmonic enhancement
Ultrahigh (210 mA/W), broadband (325-980 nm) responsivity and detectivity achieved
Enhancement from nanoparticle plasmons overlapping carrier separation region
Visible to near-infrared sensitivity ideal for color detection applications
Synergistic graphene/GaAs/plasmonics integration enables exceptional performance

Background

Graphene exhibits exceptional optoelectronic properties for broadband photodetection, yet the responsivity and detectivity of graphene-based photodetectors is constrained. Integrating graphene with semiconductors as heterostructures enhances performance, but bandgap limitations of the semiconductor restrict previous demonstrations to narrow spectral ranges unsuitable for applications demanding sensitive color detection. GaAs is an ideal candidate to overcome these limitations, with its direct 1.42 eV bandgap and high mobility enabling high-performance photodetection from the visible to near-infrared. Furthermore, the ultrafast separation of photogenerated carriers across the graphene/GaAs interface offers the potential for substantial enhancements from localized surface plasmon resonances. This work realizes a plasmon-enhanced graphene/GaAs heterojunction photodetector with simultaneously ultrahigh responsivity, detectivity and broadband response across 325-980 nm, presenting exceptional sensitivity unrivaled by existing photodetectors.

Results

Photoresponsivity and Detectivity

At 405 nm, Ag nanoparticles increased photoresponsivity by 38% to 210 mA/W and detectivity by 202% to 2.98×1013 Jones
This detectivity surpasses previous graphene-based photodetectors by 2-3 orders of magnitude
Enhancement observed across entire tested spectral range of 325 nm to 980 nm

Spectral Dependence of Enhancement

Greater enhancement occurs at shorter wavelengths, matching the Ag nanoparticle plasmon resonance peak
Demonstrates enhancement originates from surface plasmon resonance

Carrier Lifetime and EQE Analysis

Faster transient PL decay (1.65 ns vs 1.97 ns) indicates Ag nanoparticles localize light absorption near GaAs surface
Increased EQE from 300-1000 nm aligns with plasmonic enhancement
The above confirms surface plasmons enable more efficient carrier separation at the heterointerface

Optical Simulations

Simulations exhibit intense near-field concentration around Ag nanoparticles and extending into GaAs
Overlaps with graphene/GaAs junction depletion region and GaAs light absorption depth
Explains origin of exceptionally broadband enhancement in this heterosystem

Methods

The authors fabricated graphene/GaAs heterostructure photodetectors by transferring CVD-grown graphene onto n-type GaAs substrates.
Ag nanoparticles (100 nm diameter) were spin-coated onto the graphene surface to utilize surface plasmon resonance for performance enhancement.
Photocurrent, responsivity and detectivity were measured under different illumination wavelengths (325-980 nm) in self-powered mode.
Transient PL decay and EQE measurements were conducted to study the enhancement mechanism.

Conclusions

The synergy between graphene and GaAs yields a remarkable broadband enhancement through the intricate overlap of the graphene/GaAs junction depletion region, surface plasmon near field, and GaAs absorption depth. This enhancement mechanism is particularly pertinent in graphene/direct bandgap semiconductor heterostructures like graphene/GaAs. The resultant heightened responsivity, detectivity, and wide spectral range position it as an exceptional photodetector, especially for applications necessitating sensitive color detection, such as CCD imaging.

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Reference

https://www.sciencedirect.com/science/article/abs/pii/S2211285518301241?via%3Dihub