Limits...
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.


Device fabrication route and electrical characterizations.(a) Schematic design of the electron irradiation modulated graphene field effect transistor (FET); (b) Scanning electron microscope (SEM) image of the electron irradiation graphene FET, and the squared area are marked for electron irradiation. The scale bar is 10 μm ; (c) The electric characteristics as a function of gate bias of the intrinsic graphene FET, the irradiated graphene FET and the fabricated graphene p-n junction; (d) Current-voltage (I-V) curves of the same sample in (a) at room temperature with zero gate bias. The black, blue and red color lines represent measurements between electrodes 1-2, electrodes 2- 3 and electrodes 1-3 as shown in Fig. 1(b), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4495417&req=5

f1: Device fabrication route and electrical characterizations.(a) Schematic design of the electron irradiation modulated graphene field effect transistor (FET); (b) Scanning electron microscope (SEM) image of the electron irradiation graphene FET, and the squared area are marked for electron irradiation. The scale bar is 10 μm ; (c) The electric characteristics as a function of gate bias of the intrinsic graphene FET, the irradiated graphene FET and the fabricated graphene p-n junction; (d) Current-voltage (I-V) curves of the same sample in (a) at room temperature with zero gate bias. The black, blue and red color lines represent measurements between electrodes 1-2, electrodes 2- 3 and electrodes 1-3 as shown in Fig. 1(b), respectively.

Mentions: Electrical transport measurements were employed to investigate the effect of electron beam irradiation on the electronic properties of graphene FETs. As shown in Fig. 1(c,d), the pristine graphene obtained in our experiment is p-doped because of the hydrocarbon molecules or humidity absorbed on the graphene surface. In contrary, the Dirac point of electron-irradiated graphene FET shifts to the gate voltage of −20 V, as shown in Fig. 1(c), exhibiting the n-type doping of graphene. It is very obvious that, consistent with previous reports3, the on/off ratio of the graphene FET is far below conventional silicon based FET. The carrier mobility of the graphene FETs can be estimated based on the equation3: μ = dIds/dVb × L/(W × (ε0εr/d) × Vds), where L, W and d are the channel length, width and the thickness of SiO2 layer (285 nm in our devices), Vds, Ids and Vb are source-drain bias, current and bottom gate voltage, ε0 and εr are the vacuum dielectric constant and the dielectric constant of SiO2 (εr = 3.9), respectively. The mobility of the n-type region (~1500 cm2 V−1s−1) is several times lower than that of pristine graphene (~5500 cm2 V−1s−1), which might be caused by the change of carrier density and the shift of Fermi level in the graphene channel after the electron irradiation20. However, the mobility is higher than that of graphene nanostructures222324 since less edge/boundary scatterings are introduced by the electron beam irradiation method.


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)

Device fabrication route and electrical characterizations.(a) Schematic design of the electron irradiation modulated graphene field effect transistor (FET); (b) Scanning electron microscope (SEM) image of the electron irradiation graphene FET, and the squared area are marked for electron irradiation. The scale bar is 10 μm ; (c) The electric characteristics as a function of gate bias of the intrinsic graphene FET, the irradiated graphene FET and the fabricated graphene p-n junction; (d) Current-voltage (I-V) curves of the same sample in (a) at room temperature with zero gate bias. The black, blue and red color lines represent measurements between electrodes 1-2, electrodes 2- 3 and electrodes 1-3 as shown in Fig. 1(b), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Device fabrication route and electrical characterizations.(a) Schematic design of the electron irradiation modulated graphene field effect transistor (FET); (b) Scanning electron microscope (SEM) image of the electron irradiation graphene FET, and the squared area are marked for electron irradiation. The scale bar is 10 μm ; (c) The electric characteristics as a function of gate bias of the intrinsic graphene FET, the irradiated graphene FET and the fabricated graphene p-n junction; (d) Current-voltage (I-V) curves of the same sample in (a) at room temperature with zero gate bias. The black, blue and red color lines represent measurements between electrodes 1-2, electrodes 2- 3 and electrodes 1-3 as shown in Fig. 1(b), respectively.
Mentions: Electrical transport measurements were employed to investigate the effect of electron beam irradiation on the electronic properties of graphene FETs. As shown in Fig. 1(c,d), the pristine graphene obtained in our experiment is p-doped because of the hydrocarbon molecules or humidity absorbed on the graphene surface. In contrary, the Dirac point of electron-irradiated graphene FET shifts to the gate voltage of −20 V, as shown in Fig. 1(c), exhibiting the n-type doping of graphene. It is very obvious that, consistent with previous reports3, the on/off ratio of the graphene FET is far below conventional silicon based FET. The carrier mobility of the graphene FETs can be estimated based on the equation3: μ = dIds/dVb × L/(W × (ε0εr/d) × Vds), where L, W and d are the channel length, width and the thickness of SiO2 layer (285 nm in our devices), Vds, Ids and Vb are source-drain bias, current and bottom gate voltage, ε0 and εr are the vacuum dielectric constant and the dielectric constant of SiO2 (εr = 3.9), respectively. The mobility of the n-type region (~1500 cm2 V−1s−1) is several times lower than that of pristine graphene (~5500 cm2 V−1s−1), which might be caused by the change of carrier density and the shift of Fermi level in the graphene channel after the electron irradiation20. However, the mobility is higher than that of graphene nanostructures222324 since less edge/boundary scatterings are introduced by the electron beam irradiation method.

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.