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  • 學位論文

石墨烯於量子井紅外線光偵測器及熱電子電晶體的增益

Performance enhancements by graphene integration on multicolor quantum grid infrared photodetectors and hot electron transistors.

指導教授 : 管傑雄
共同指導教授 : 藍彥文(Yann-Wen Lan)

摘要


石墨烯(graphene)由於其單原子層結構,超高的電子遷移率與寬頻的吸收頻譜使其在光學元件及高頻元件中的上備受重視。本研究探討石墨烯對於量子井紅外光偵測器和熱電子晶體的效能增益。 首先在量子井紅外線光偵測器方面,我們利用石墨烯與半導體介面形成的蕭特機能障(Schottky barrier)來做光電二極體產生光電流,進而使光偵測器的效能提升。本研究還探討超晶格的組合以及光柵結構提升元件的效能與吸收頻譜,製作成石墨烯覆蓋的多彩量子井網格紅外光偵測器(multicolor quantum grid infrared photodetector ,QGIP)。歸功於與超晶格的結構,元件提供可調控的吸收光譜。而從響應度方面,由於石墨烯與半導體介面形成的光電二極體所提供額外光電流,使其響應度跟標準片相比可以大幅度的提高。本研究亦藉由模擬最佳化的光柵結構使員建在響應度上沒有帶大的變化下使暗電流大幅降低。因為上述的效能提升,石墨烯覆蓋的多彩量子井網格紅外光電探測器的偵測率能飛越性的提高。接下來我們更進一步研究了石墨烯與砷化鎵形成的蕭特機能障使超晶格彎曲來使光訊號更佳的提升。使偵測率能更進一步的增加。 而石墨烯熱電子電晶體方面,本論文探討了利用雙層氧化層(TiO2/HfO2) 作為熱電子電晶體的基極(base)與集極(collector)間的穿隧勢壘(tunneling barrier)以及在大氣下成長,數個奈米的二氧化矽作為射極與基極的穿隧勢壘的方法,來改善傳統石墨烯熱電子體低熱電子穿隧機率與漏電的問題。並且更進一步的利用多種二維材料的疊合(MoS2/h-BN)取代傳統氧化層作為基極與集極間的穿隧勢壘,更加的提升元件的性能。在直流量測方面,元件表現極高的電流密度(~ 200 A/cm2 ),共基極電流增益( ~99.2%),與共射極電流增益 (common emitter current gain ~3)。由於這些直流特性的改善,石墨烯熱電子電晶體能操作在數十吉赫茲(GHz)左右。 本研究展示了藉由石墨烯等二維材料與半導體元件的垂直傳輸結構,能大幅度的改善傳統量子井紅外線光偵測器與熱電子電晶體的效能,而這些成果亦提供成為實現下一世代更光電元件與高頻元件的重要實驗基礎。

並列摘要


Graphene is highly valued in optical components and high-frequency devices due to its single atomic layer structure, ultra-high electron mobility, and broadband absorption spectrum. This study explores the performance gains of graphene for quantum well infrared detectors and hot electron transistors. In the quantum well infrared photodetector detector, we use the Schottky barrier formed by the graphene and GaAs as a photodiode to generate photocurrent, thereby improving the responsivity of quantum well infrared photodetector detector. This research also explores the integration of superlattices and the grating structure to enhance the efficiency and absorption spectrum of quantum well infrared photodetector detectors and fabricated a graphene-covered multicolor quantum grid infrared photodetector. Thanks to the superlattice structure, the absorption spectrum can be controlled by applied bias. In terms of responsivity, due to the additional photocurrent provided by graphene/GaAs intersurface, the responsivity can be significantly improved from the standard QWIP sample. This study also demonstrates the simulation of the optimized grating structure to reduce the dark current without attenuation in the responsivity. As a result, the detectivity of the graphene-covered multicolor quantum well grid infrared photodetector can be dramatically improved. Moreover, we studied the Schottky barrier formed by graphene and gallium arsenide to bend the superlattice to improve the optical signal. The performance of QWIPcan is further increased. About the graphene base hot electron transistor, this thesis discusses the double-layer oxide layer (TiO2/HfO2) as the tunneling barrier between the base and collector of the hot electron transistor. Native silicon dioxide is used as the tunneling barrier between the emitter and the base. These two tunneling barriers increase the low thermionic tunneling probability and leakage current in the traditional graphene base hot electron transistor. Moreover, the further studies are about a variety of two-dimensional material stacks (MoS2/h-BN) to replace the traditional oxide layer as the tunnel barrier between the base and collector to improve the device's performance further. In terms of DC measurement, the device exhibits extremely high current density (~ 200 A/cm2), common base current gain (~99.2%), and common emitter current gain (~3). Due to these improvements in DC characteristics, graphene hot electron transistors can operate at around tens of gigahertz. This research demonstrates the realization of the structure of graphene and other materials and semiconductor components, which can cultivate quantum well infrared photodetector and hot electron transistor. These results also provide an important experimental result to realize the next generation’s photoelectric devices and high-frequency components.

參考文獻


References
1 Trushin, M. Theory of photoexcited and thermionic emission across a two-dimensional graphene-semiconductor Schottky junction. Physical Review B 97, 195447 (2018).
2 Di Bartolomeo, A. Graphene Schottky diodes: An experimental review of the rectifying graphene/semiconductor heterojunction. Physics Reports 606, 1-58 (2016).
3 Li, X. Zhu, H. The graphene-semiconductor Schottky junction. Physics Today 69, 46-51 (2016).
4 Koppens, F. et al. Photodetectors based on graphene, other two-dimensional materials, and hybrid systems. Nature nanotechnology 9, 780 (2014).

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