Type-II HfS2/MoS2 Heterojunction Transistors

Seiko NETSU  Toru KANAZAWA  Teerayut UWANNO  Tomohiro AMEMIYA  Kosuke NAGASHIO  Yasuyuki MIYAMOTO  

IEICE TRANSACTIONS on Electronics   Vol.E101-C   No.5   pp.338-342
Publication Date: 2018/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.338
Type of Manuscript: BRIEF PAPER
TMDC,  MoS2,  HfS2,  tunnel FET,  heterojunction,  

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We experimentally demonstrate transistor operation in a vertical p+-MoS2/n-HfS2 van der Waals (vdW) heterostructure configuration for the first time. The HfS2/MoS2 heterojunction transistor exhibits an ON/OFF ratio of 104 and a maximum drain current of 20 nA. These values are comparable with the corresponding reported values for vdW heterojunction TFETs. Moreover, we study the effect of atmospheric exposure on the subthreshold slope (SS) of the HfS2/MoS2 transistor. Unpassivated and passivated devices are compared in terms of their SS values and IDS-VGS hysteresis. While the unpassivated HfS2/MoS2 heterojunction transistor exhibits a minimum SS value of 2000 mV/dec, the same device passivated with a 20-nm-thick HfO2 film exhibits a significantly lower SS value of 700 mV/dec. HfO2 passivation protects the device from contamination caused by atmospheric moisture and oxygen and also reduces the effect of surface traps. We believe that our findings will contribute to the practical realization of HfS2-based vdW heterojunction TFETs.