Mobility Anisotropy in Black Phosphorus MOSFETs With HfO2; Gate Dielectrics

Nazila Haratipour, Yue Liu, Ryan J. Wu, Seon Namgung, P. Paul Ruden, K. Andre Mkhoyan, Sang Hyun Oh, Steven J. Koester

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Precise measurements of the mobility anisotropy along high-symmetry crystal axes in black phosphorus (BP) MOSFETs are reported. Locally back-gated BP MOSFETs with 13-nm HfO2 dielectric and channel length ranging from 0.3 to 0.7 μm are fabricated. A single BP flake of a uniform thickness is exfoliated and etched along armchair (AC) and zigzag (ZZ) crystal axes, and the orientations are confirmed using optical and transmission electron microscopy analyses. The hole and electron mobilities along each direction are extracted using the transfer length method. The AC-to-ZZ hole mobility ratio is found to increase from 1.4 (1.5) to 2.0 (2.9) as the sheet concentration increased from 5.1× 1011 to 1.9× 1012 cm-2 at room temperature (77 K). The room-temperature electron mobility anisotropy is found to be similar to that for holes with an AC-to-ZZ mobility ratio increasing from 1.4 to 2.1 from 5.1× 1011 to 1.9× 1012 cm-2 though electrons showed only a very weak temperature dependence. A Boltzmann transport model is used to explain the concentration- and temperature-dependent mobility anisotropies which can be well described using a charge center scattering model.

Original languageEnglish (US)
Article number8454856
Pages (from-to)4093-4101
Number of pages9
JournalIEEE Transactions on Electron Devices
Volume65
Issue number10
DOIs
StatePublished - Oct 2018

Bibliographical note

Funding Information:
Manuscript received April 25, 2018; revised June 30, 2018 and August 4, 2018; accepted August 5, 2018. Date of publication September 5, 2018; date of current version September 20, 2018. The work of Nazila Haratipour, Ryan J. Wu, K. Andre Mkhoyan, Sang-Hyun Oh, and Steven J. Koester was supported by the National Science Foundation (NSF) through the University of Minnesota MRSEC under Award DMR-1420013. The work of Seon Namgung and Steven J. Koester was supported by the Air Force Office of Scientific Research under Award FA9550-14-1-0277. The work of Sang-Hyun Oh was supported by NSF under Award ECCS-1610333. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the NSF through the National Nanotechnology Coordinated Infrastructure under Award Number ECCS-1542202. The review of this paper was arranged by Editor S. Das. (Corresponding author: Steven J. Koester.) N. Haratipour and Y. Liu were with the Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA. They are now with Intel Corporation, Hillsboro, OR 97124 USA.

Publisher Copyright:
© 1963-2012 IEEE.

Keywords

  • Anisotropy
  • black phosphorus (BP)
  • mobility
  • MOSFETs
  • phosphorene.

How much support was provided by MRSEC?

  • Partial

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