Electrical characteristics of multilayer MoS2 FETs with MoS 2/graphene heterojunction contacts

Joon Young Kwak, Jeonghyun Hwang, Brian Calderon, Hussain Alsalman, Nini Munoz, Brian Schutter, Michael G. Spencer

Research output: Contribution to journalArticlepeer-review

178 Scopus citations

Abstract

The electrical properties of multilayer MoS2/graphene heterojunction transistors are investigated. Temperature-dependent I-V measurements indicate the concentration of unintentional donors in exfoliated MoS2 to be 3.57 × 1011 cm-2, while the ionized donor concentration is determined as 3.61 × 1010 cm-2. The temperature-dependent measurements also reveal two dominant donor levels, one at 0.27 eV below the conduction band and another located at 0.05 eV below the conduction band. The I-V characteristics are asymmetric with drain bias voltage and dependent on the junction used for the source or drain contact. I-V characteristics of the device are consistent with a long channel one-dimensional field-effect transistor model with Schottky contact. Utilizing devices, which have both graphene/MoS2 and Ti/MoS2 contacts, the Schottky barrier heights of both interfaces are measured. The charge transport mechanism in both junctions was determined to be either thermionic-field emission or field emission depending on bias voltage and temperature. On the basis of a thermionic field emission model, the barrier height at the graphene/MoS2 interface was determined to be 0.23 eV, while the barrier height at the Ti/MoS2 interface was 0.40 eV. The value of Ti/MoS2 barrier is higher than previously reported values, which did not include the effects of thermionic field emission.

Original languageEnglish
Pages (from-to)4511-4516
Number of pages6
JournalNano Letters
Volume14
Issue number8
DOIs
StatePublished - 13 Aug 2014

Keywords

  • barrier height
  • donor level
  • graphene
  • Heterojunction
  • ionized impurity

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