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S.S.H
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Outline
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Introduction
Experiments
Results and Discussion
Conclusion
References
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Introduction
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Two-dimensional Graphene has attracted considerable attention
recently due to its unique properties such as
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high carrier mobility ~ (15000 cm2 /s)
broad spectral absorption
low optical absorption rate ~(2.3%)
short carrier lifetime
Small band gap ~ (0ev~0.25ev)
ultrafast response time ~ (1.5 ps)
as well as mechanical flexibility.
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Introduction
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The heterojunctions of graphene with traditional semiconductor
materials can be used to construct various functional devices, such
as :
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With Si to produce diodes
Photodetectors
So-called “barristor;” with monolayer MoS2 and WS2 to
form vertical field effect transistors
With ZnO nanowire to fabricate UV detectors
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Introduction
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In this work, we report the graphene/GaN diodes for UV and
visible photodetectors with large photoresponsive area. The
physical mechanisms are discussed by considering the variation of
the Schottky barrier at the graphene/GaN interface with photoillumination.
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Experiments
100nm thick
FIG. 1. (a) Schematic diagram of the device structure. (b) Optical
image of a typical device.
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Results and Discussion
361 nm
Source1: He–Cd laser~ (325nm)
Source2: Green laser~ (514nm)
Spot size: ~ (2μm)
FIG. 1. (c) Photoluminescence spectrum of the GaN film. (d) Raman
spectrum of the single layer graphene.
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Results and Discussion
100𝝁𝐦/𝛍𝒎𝟐
(log)
100% laser power
Source: 325nm UV laser
 Current on/off ratio
10V and -10
I (light) / I (dark) → 56 and 1820
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Results and Discussion
Shocktty Barrier hight
In Dark = 0.49ev
接觸面積
理查德森常數
GaN= 27.9 A cm−2 K−2
n：理想因子(ideality factor)
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Elementary charge (q) = 1.60217733 10−19 C
Boltzmann constant (k) = 1.380658 10-23 J/T
Electro affinity of GaN is 4.1ev
Work function of grapgene is 4.6ev
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Results and Discussion
 Current on/off ratio Under reverse bias
I (light) / I (dark) → ~ 103
Source: 514nm Green laser
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Results and Discussion
Power law =
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Results and Discussion
FIG. 5. Multi-cycle photocurrent response to incident (a) UV and (b) green light under bias
voltage of 10 V. Photoelectric responses by chopping light with (c) 800 Hz for UV light and (d)
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100 Hz for green light.
Results and Discussion
The extraction of the rising and decay time constants for (e) UV light and (f) green
light.
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Results and Discussion
2.62 (ev) 光子能量
Fowler 發射係數
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Conclusion
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The barrier height can be effectively tuned by incident UV laser
with different light powers, and thus the photoconductance is
changed accordingly.
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The devices show a photoelectric response with millisecond rising
and decaying time constants, paving an alternative route towards
broadband photodetectors with large photoresponsive area.
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References
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Layer-by-layer assembly of vertically conducting graphene devices (JingJing Chen,Jie Meng,Yang-Bo Zhou,Han-Chun Wu,Ya-Qing Bie,Zhi-Min
Liao&Da-Peng Yu
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Graphene Barristor, a Triode Device with a Gate-Controlled Schottky
Barrier, Heejun Yang, Jinseong Heo, Seongjun Park,1 Hyun Jae Song,
David H. Seo, Kyung-Eun Byun, Philip Kim, InKyeong Yoo, Hyun-Jong
Chung, Kinam Kim
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Thank you for your attention
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