Black phosphorus (BP) has recently emerged as a promising narrow band gap layered semiconductor with optoelectronic properties that bridge the gap between semimetallic graphene and wide band gap transition metal dichalcogenides such as MoS2. To date, BP field-effect transistors have utilized a lateral geometry with in-plane transport dominating device characteristics. In contrast, we present here a vertical field-effect transistor geometry based on a graphene/BP van der Waals heterostructure. The resulting device characteristics include high on-state current densities (>1600 A/cm2) and current on/off ratios exceeding 800 at low temperature. Two distinct charge transport mechanisms are identified, which are dominant for different regimes of temperature and gate voltage. In particular, the Schottky barrier between graphene and BP determines charge transport at high temperatures and positive gate voltages, whereas tunneling dominates at low temperatures and negative gate voltages. These results elucidate out-of-plane electronic transport in BP and thus have implications for the design and operation of BP-based van der Waals heterostructures.
Bibliographical noteFunding Information:
This research was supported by the NSF Materials Research Science and Engineering Center (MRSEC) of Northwestern University (DMR-1121262), the NSF EFRI 2-DARE program (NSF EFRI-143510), and the Office of Naval Research (N00014-14-1-0669). J.K. acknowledges support from the Postdoctoral Research Program of Sungkyunkwan University. D.J. acknowledges additional support from an SPIE education scholarship and IEEE DEIS fellowship. This work made use of the Northwestern University Micro/Nano Fabrication Facility (NUFAB) as well as the Northwestern University Atomic and Nanoscale Characterization Experimental Center (NUANCE), which has received support from the MRSEC (NSF DMR-1121262), State of Illinois, and Northwestern University.
© 2016 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering