Switchable photovoltaic and photoconductivity behaviors in layer-modified MoS2 heterojunction phototransistors
Fu-Yu Shih1,2*, Yueh-Chun Wu1, Min-Chuan Shih3, Yi-Hsiang Shih2, Ya-Ping Chiu3, Chun-Wei Chen4, Yang-Fang Chen2, Wei-Hua Wang1
1Institute of Atomic and molecular Sciences, Academia Sinica, Taipei, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3Department of Physics, National Taiwan Normal University, Taipei, Taiwan
4Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan
* presenting author:Fu-Yu Shih, email:fu.yu.shih@gmail.com
The electronic band structures of two-dimensional transition-metal dichalcogenides (TMDCs) critically depend on the number of layers, therefore offering a distinct approach for designing novel device structures. The optical band gap of molybdenum disulfide (MoS2) can vary from 1.9 eV (monolayer) to 1.3 eV (bulk), giving a wide energy range for tuning the band gap. However, the properties of interface between thinner and thicker layers of MoS2 are not fully understood. In this work, we fabricated MoS2 junction devices with different number of layers to study their energy profile and optoelectronic properties. Type-I heterojunction was determined by performing scanning tunneling microscope measurement. The photovoltaic and photoconductivity behaviors are tunable by controlling the external source drain bias. The photoresponse study suggests that the tunability of the photoresponse at interface of MoS2 junction is attributed to alteration between intrinsic and extrinsic photodetection mechanisms. The study of device physics of MoS2 junction shows the promises of utilizing TMDCs–based materials for future electronic and optoelectronic applications.

Keywords: molybdenum disulfide (MoS2), optoelectronics, two-dimensional materials