S.S.H 1

Outline Introduction Experiments Results and Discussion Conclusion References 2

Introduction 3

The heterojunctions of graphene with traditional semiconductor materials can be used to construct various functional devices, such as : With Si to produce diodes ‚Photodetectors ƒSo-called “barristor;” with monolayer MoS 2 and WS 2 to form vertical field effect transistors „With ZnO nanowire to fabricate UV detectors 4

Introduction 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 photo- illumination. 5

Experiments 100nm thick FIG. 1. (a) Schematic diagram of the device structure. (b) Optical image of a typical device. 6

Results and Discussion FIG. 1. (c) Photoluminescence spectrum of the GaN film. (d) Raman spectrum of the single layer graphene. Source1: He–Cd laser~ (325nm) Source2: Green laser~ (514nm) Spot size: ~ (2μm) 361 nm 7

Results and Discussion Source: 325nm UV laser 100% laser power (log) 8  Current on/off ratio 10V and -10 I (light) / I (dark) → 56 and 1820

Results and Discussion 接觸面積 Shocktty Barrier hight In Dark = 0.49ev 9 n ：理想因子 (ideality factor)

Results and Discussion Source: 514nm Green laser 10

Results and Discussion Power law = 11

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) 100 Hz for green light. 12

Results and Discussion The extraction of the rising and decay time constants for (e) UV light and (f) green light. 13

Results and Discussion Fowler 發射係數 (ev) 光子能量

Conclusion The barrier height can be effectively tuned by incident UV laser with different light powers, and thus the photoconductance is changed accordingly. The devices show a photoelectric response with millisecond rising and decaying time constants, paving an alternative route towards broadband photodetectors with large photoresponsive area. 15

References Layer-by-layer assembly of vertically conducting graphene devices (Jing- Jing Chen,Jie Meng,Yang-Bo Zhou,Han-Chun Wu,Ya-Qing Bie,Zhi-Min Liao&Da-Peng Yu 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 16

Thank you for your attention 17