Two-Dimensional Materials Inserted at the Metal/Semiconductor Interface: Attractive Candidates for Semiconductor Device Contacts

Abstract

Metal-semiconductor junctions are indispensable in semiconductor devices, but they have recently become a major limiting factor precluding device performance improvement. Here, we report the modification of a metal/n-type Si Schottky contact barrier by the introduction of two-dimensional (2D) materials of either graphene or hexagonal boron nitride (h-BN) at the interface. We realized the lowest specific contact resistivities (ρ) of 3.30 nΩ cm (lightly doped n-type Si, ∼ 10/cm) and 1.47 nΩ cm (heavily doped n-type Si, ∼ 10/cm) via 2D material insertion are approaching the theoretical limit of 1.3 nΩ cm. We demonstrated the role of the 2D materials at the interface in achieving a low ρ value by the following mechanisms: (a) 2D materials effectively form dipoles at the metal-2D material (M/2D) interface, thereby reducing the metal work function and changing the pinning point, and (b) the fully metalized M/2D system shifts the pinning point toward the Si conduction band, thus decreasing the Schottky barrier. As a result, the fully metalized M/2D system using atomically thin and well-defined 2D materials shows a significantly reduced ρ. The proposed 2D material insertion technique can be used to obtain extremely low contact resistivities in metal/n-type Si systems and will help to achieve major performance improvements in semiconductor technologies.

Efficient Charge Separation in 2D Janus van der Waals Structures with Built-in Electric Fields and Intrinsic p–n Doping

“…We mention that other applications of (stacked) 2D Janus structures could be envisioned such as the tunnel diodes, e.g., to separate light-absorbing layers in multijunction solar cells, tunnel field-effect transistors, 44 or for tuning band alignment or Schottky barriers in van der Waals heterostructures. 45 Finally, we show that finite out-of-plane dipole moments in 2D materials are not limited to the MoSSe monolayer. We have performed DFT calculations for a number of monolayers with similar structures and chemical compositions to MoSSe.…”

A low Schottky barrier height and transport mechanism in gold–graphene–silicon (001) heterojunctions

“…As they are ultimately thin, 2D crystals would reduce the resistance increase due to insulator barriers and tune the work function. 5,6 Graphene (G), a one-atom-thick layer of carbon in a honeycomb crystal lattice, avoids the formation of undesired interface states and/ or metal induced states at the Si surface. 7,8 Moreover, the work function of graphene can be modulated by doping with various metals.…”

Impermeable Graphene Oxide Protects Silicon from Oxidation

“…The highly conducting ohmic contact of the Si–rGO x surface is attributed to both the dipole moment dictated by the Si–O bonds at the surface and the interfacial material (rGO x ), which is much more conducting than GO x . Therefore, rGO x enhances the current flow at the interface. − The I – V measurements re-emphasize that the GO x layers protect Si from inorganic oxides. Inorganic oxides are highly insulating (band gap of 8–9 eV) and cannot be electrochemically reduced in an accessible potential window (Figure d–f).…”