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Photocurrent generation in lateral graphene p-n junction created by electron-beam irradiation.

Yu X, Shen Y, Liu T, Wu TT, Jie Wang Q - Sci Rep (2015)

Bottom Line: Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential.The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 10(10) Jones (cm Hz(1/2) W(-1)) at room temperature, which is on a par with that of the traditional III-V photodetectors.The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

View Article: PubMed Central - PubMed

Affiliation: OPTIMUS, Photonics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Ave., 639798, Singapore.

ABSTRACT
Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 10(10) Jones (cm Hz(1/2) W(-1)) at room temperature, which is on a par with that of the traditional III-V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

No MeSH data available.


Related in: MedlinePlus

Photodetection using the p-n homo-junction graphene FET.(a) Time dependent photocurrent measurement on the sample irradiated for 30 s with 633 nm laser (4 μW); (b) Power dependence of the photocurrent with 532 nm (black curve) and 633 nm (red curve) lasers; (c) Photocurrent measured in one period of modulation with the 633 nm laser illumination; (d) Photoresponse and decay time measurements of graphene with different Fermi levels, corresponding to different irradiation times as shown in Fig. 4(b).
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f5: Photodetection using the p-n homo-junction graphene FET.(a) Time dependent photocurrent measurement on the sample irradiated for 30 s with 633 nm laser (4 μW); (b) Power dependence of the photocurrent with 532 nm (black curve) and 633 nm (red curve) lasers; (c) Photocurrent measured in one period of modulation with the 633 nm laser illumination; (d) Photoresponse and decay time measurements of graphene with different Fermi levels, corresponding to different irradiation times as shown in Fig. 4(b).

Mentions: The potential barrier built here is the force driving the separation and transportation of photo-excited electron-hole pairs and facilitates the optoelectronic applications of graphene. Figure 5(a) shows the time-dependent switching cycles of photoresponse measurement with sample 30 s irradiated samples as a demonstration at zero source-drain bias and zero gate voltage under global illumination on the whole device. The responsivity for the devices measured under a laser illumination at 633 nm is around 5 mA/W, which is higher than that obtained in the graphene/metal Schottky junction photodetectors. The photoresponse can be expressed by a power law IPC = CPγ (C is a constant and P is the illumination power) as shown in Fig. 5(b). For the laser with the wavelength of 533 nm and 633 nm, γ is 0.74 and 0.78, respectively, indicating that the recombination kinetics of photocarriers involves both traps states and interactions between photogenerated carriers33. The decrease of the photocurrent with the incident laser power can be attributed to the reduction of the numbers of photogenerated carriers available for extraction under high photon flux due to the Auger process or the saturation of recombination/trap states that influence the lifetime of the generated carriers3435. The external quantum efficiency of ~10% for this device is mainly limited by the insufficient absorption of incident light and the trapping and recombination of carriers as the created potential barrier is relatively small. Further increase of the barrier potential by increasing irradiation time may significantly boast the photoresponsivity and response time as shown in Fig. 5(d). On the other hand, the defect and vacancy play an essential role in the response speed of the photodetector. As shown in Fig. 5(c,d), the decay time increases with the upshift of Fermi level that represents the increase of defect density, indicating that the irradiation induced localized states leads to carrier scattering and decreases the carrier mobility. Though the response speed is slower than pure graphene photodetectors with a response time in the picosecond level, the response time and decay time are still shorter than the nanostructured disordered graphene photodetectors53336 in which the response speed is around hundreds of seconds caused by the defect/edge scatterings and recombinations.


Photocurrent generation in lateral graphene p-n junction created by electron-beam irradiation.

Yu X, Shen Y, Liu T, Wu TT, Jie Wang Q - Sci Rep (2015)

Photodetection using the p-n homo-junction graphene FET.(a) Time dependent photocurrent measurement on the sample irradiated for 30 s with 633 nm laser (4 μW); (b) Power dependence of the photocurrent with 532 nm (black curve) and 633 nm (red curve) lasers; (c) Photocurrent measured in one period of modulation with the 633 nm laser illumination; (d) Photoresponse and decay time measurements of graphene with different Fermi levels, corresponding to different irradiation times as shown in Fig. 4(b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495417&req=5

f5: Photodetection using the p-n homo-junction graphene FET.(a) Time dependent photocurrent measurement on the sample irradiated for 30 s with 633 nm laser (4 μW); (b) Power dependence of the photocurrent with 532 nm (black curve) and 633 nm (red curve) lasers; (c) Photocurrent measured in one period of modulation with the 633 nm laser illumination; (d) Photoresponse and decay time measurements of graphene with different Fermi levels, corresponding to different irradiation times as shown in Fig. 4(b).
Mentions: The potential barrier built here is the force driving the separation and transportation of photo-excited electron-hole pairs and facilitates the optoelectronic applications of graphene. Figure 5(a) shows the time-dependent switching cycles of photoresponse measurement with sample 30 s irradiated samples as a demonstration at zero source-drain bias and zero gate voltage under global illumination on the whole device. The responsivity for the devices measured under a laser illumination at 633 nm is around 5 mA/W, which is higher than that obtained in the graphene/metal Schottky junction photodetectors. The photoresponse can be expressed by a power law IPC = CPγ (C is a constant and P is the illumination power) as shown in Fig. 5(b). For the laser with the wavelength of 533 nm and 633 nm, γ is 0.74 and 0.78, respectively, indicating that the recombination kinetics of photocarriers involves both traps states and interactions between photogenerated carriers33. The decrease of the photocurrent with the incident laser power can be attributed to the reduction of the numbers of photogenerated carriers available for extraction under high photon flux due to the Auger process or the saturation of recombination/trap states that influence the lifetime of the generated carriers3435. The external quantum efficiency of ~10% for this device is mainly limited by the insufficient absorption of incident light and the trapping and recombination of carriers as the created potential barrier is relatively small. Further increase of the barrier potential by increasing irradiation time may significantly boast the photoresponsivity and response time as shown in Fig. 5(d). On the other hand, the defect and vacancy play an essential role in the response speed of the photodetector. As shown in Fig. 5(c,d), the decay time increases with the upshift of Fermi level that represents the increase of defect density, indicating that the irradiation induced localized states leads to carrier scattering and decreases the carrier mobility. Though the response speed is slower than pure graphene photodetectors with a response time in the picosecond level, the response time and decay time are still shorter than the nanostructured disordered graphene photodetectors53336 in which the response speed is around hundreds of seconds caused by the defect/edge scatterings and recombinations.

Bottom Line: Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential.The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 10(10) Jones (cm Hz(1/2) W(-1)) at room temperature, which is on a par with that of the traditional III-V photodetectors.The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

View Article: PubMed Central - PubMed

Affiliation: OPTIMUS, Photonics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Ave., 639798, Singapore.

ABSTRACT
Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 10(10) Jones (cm Hz(1/2) W(-1)) at room temperature, which is on a par with that of the traditional III-V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

No MeSH data available.


Related in: MedlinePlus